bigbywolfe

I disagree. 
 
Granted, it's a limitation, sure. 
 
But look at the power builds it gets applied to.  Shrike posted a 30 DC Killing Attack above. 
 
I don't know what the parameters are for the campaign from which that spell is pulled, but I can absolutely _guarantee_ that a 30 DC Killing Attack _will_ kill every living thing in any fantasy campaign I have ever run, including dragons and lesser gods. Given this, I'd have a hard time assigning it much more than a - 1/2 (again, in that particular world). 
 
I am _not_ looking to derail an interesting thread, but it bears mentioning that the book value for limitations is not particularly helpful without a published game world that includes some guidelines, limits, averages, etc. 
 
Otherwise, we are left to extrapolate from the values given.  In the spell Shrike posted, we're looking at a seriously high-powered world where we can expect a 30 DC attack to kill outright only 1/3 of the time. 

A KA that Does No Stun and has IPE to Target Effects (+1 - neither the target nor anyone else can perceive the damage done) would weaken characters with multiple uses, but no one could see that the target is down BOD.  Now that's a curse!
 
Maybe it's AVAD/NND, Does BOD as well?
 
 
Recalling the source material, I am trying to remember a significant character who was killed by the Killing Curse.  I think that's how Snape went, caught entirely unaware.  Probably Dumbledore as well - killed by the specific person he had requested kill him.  Seems like this should be pretty unlikely to work against anyone of PC/major NPC status.  That is, if we want to model it in a manner which is consistent with the source material...
 
Harry, but he survived - so much for "all or nothing" - perhaps he had the NND defense, but he still took damage.
 
EDIT: Most of the victims down at the bottom of https://harrypotter.fandom.com/wiki/Killing_Curse were either offscreen, minor characters or accidental victims when the caster missed.

I don't feel that "Boop, character's over" has any place in a TTRPG.  Including sudden death will just discourage players from becoming attached to their characters and NPCs.  Genre shmenre, if I heard a GM talking about "you just die" effects I'd walk.  No way am I investing effort into something that ends at the whim of 3d6. 

I've always been of the opinion that anti-power powers need to be targeting either something universal (ED, SPD, Running) or a SFX (magic, fire, body-alteration) to make sense. 

Presumably a superhero campaign? Could you post more information on the setting, genre, # of points, etc?
 
 
Limitations such as this are subject to GM interpretation. 
 
If your interpretation is, there's some shadows somewhere in the scene and therefore such abilities work nearly all of the time, then yeah it's not very limiting.
 
If you interpret it as personal powers with the lim only work if the character themselves is in shadow, and targeted abilities only work if the character themselves and their target are in shadow it gets more restrictive quickly.
 
You could further interpret it that for non-indirect targeted powers there must also be shadow between the character and the target. That would be quite restrictive.
 
Also, there is the matter of how you are defining the lim in the first place. By "Darkness" do you literally mean the POWER Darkness or do you just mean "areas with low to no natural light"? I'm assuming the later...you mean poor to no lighting conditions.
 
Mechanically "Night" in the Hero System is basically a label for a -4 Sight PER penalty; shadows / poor lighting conditions are similarly just -1 to -3 Sight PER penalties.
 
Similarly, areas of good lighting are defined as bonuses to Sight PER checks.
 
Fundamentally, light and the absence of light as we colloquially think of them in the real world are represented in the Hero System as PER modifiers.
 
The Darkness power on the other hand is impenetrable / opaque to the targeted sense group; it has nothing to do with PER checks and basically nullifies / turns off PER checks for the affected senses across its area. Also, despite the name, a given Darkness based power affecting the Sight Group may not necessarily have the SFX of "lack of light"; it could have the SFX of a magical spell, or sensory overload, or a mental power (blocking the mind's ability to process visual input), or smoke, or whatever. If a target were in a "Dazzling Disarray of D'Azzario" spell which blinded targets with mystical scintillating prismatic sparkly bits...bought as Darkness vs Sight Group, there is no SFX of "no light"...quite the opposite, the SFX calls for brightness. 
 
Coming back around to your situation, if you rephrase the limitation as "Only in Poor Lighting Conditions" rather than "Only in Darkness / Shadows", then it becomes relatively easy to mechanically adjudicate when the limitation does and does not apply...if a normal person would not suffer -1 or more to a sight based PER check to perceive the character or the target due to poor lighting, the limitation applies. If they would suffer at least -1 to PER check to perceive the character / target, the lim does not apply and the power works. Easy to adjudicate.
 
 
Your instinct is correct in having some concerns about this power. 
 
However the thing that stands out as problematic to me on this particular build is first and foremost that it is 0 END.
 
0 END on Constant attack powers is pretty much always an issue. As soon as someone slaps 0 END on a Constant Attack power, I mentally upgrade the power to a YIELD sign if it isn't already one, and a STOP sign if it is.
 
Usable On Others is a STOP sign advantage already. Usable As Attack is even more uber than that; even on an already STOP sign ability the rules explicitly re-stipulate "Because Usable As Attack powers can be extremely effective, the GM must approve them". Smacking 0 END on top of that should get something like a RADIOACTIVE sign next to it. 
 

 
With this sort of ability, if I allow it at all I typically make players define a reasonable off-switch, something that will turn the ability off or block it in the first place. There must be some kind of control over it. In this case the power isn't Uncontrolled, so staggering / KO'ing the character will turn it off, as will breaking Line of Sight between the target and the character. That's something, but mano y mano it often wont make a difference to the victim if they can't target the character and can't perceive their area well enough to deliberately move out of Line of Sight.
 
I would require the player to tweak that build slightly to make it less of a soft lock. 
 
I would look at the character's origin of powers and specific SFX first and try to derive some sensible restriction on such abilities stemming from the nature of the character's abilities. If nothing presented itself there I would then turn to the mechanics to nerf it a bit. I might only permit the player to take it at 1/2 END, for instance. Or perhaps place some limits around frequency of use...if this character can spam the attack it's obviously much more problematic, but if it takes time or comes at some cost to activate it then it will be less frequently used and thus less of a problem. But long story short, I would want that ability tweaked to put a leash on it before I allowed it into play.

They basically are the same already; 3d6 roll under with situational modifiers.
 
In the case of an attack roll it is resisted by the opponent's DCV, vs the typically unresisted nature of skill rolls...but the resistance of the target's DCV is really just a penalty to the 11- + bonuses roll made by the attacker and is thus the same as say a Acrobatics roll with a situational penalty.
 

I got the cards and they look great! I haven’t gotten through all of them yet. Some to be honest I’m not as thrilled with and felt could’ve been done better. Better in the sense of ease of play. Two off my head Science! and Super Biw and Arrows. Science because it’s what 10 empty science skills. I couldn’t name off that many off the top off my head during play. This card I think works as better as fewer slots with a higher bonus to each skill or as a massively large general Science skill and eachbwith a note that the player takes a penalty to skill roll for specific science question. The Suoer Bow is just listed as a MP but nothing listed. The throwing item (?) has at least 3 slot MP filled out. (Blast, KA and Entangle) whichbworks for Super Bow. Again in play the card itself doesn’t help, you’d have to have it figured out before hand.  I still like the concept though. Perhaps they’ll come out with a third deck. Perhaps it could be player suggestions?
 
 

trying this on my phone...
 
Yep.  Now on missle weapons and staying with the idea of lizardmen with a prehensile tail.  One of Michael Moorcock's Elric books they had a enemy that used obsidian discs throw using a wooden throwing stick I think was modelled from the atl-atl. 
 
So...
The terrain is extremely rugged broken rocky desert with many ravines that prohibit traditional formation fighting.  Hunters rarely have a second shot whwn hunting prey animals so cunning and accuracy are the key traits of the successful hunter.  This carries over to warfare.  Warriors prefer stout narrow sheilds built of hide centered on a warclub two or three feet in length and a short spear/sword (think the shorter version of the assagai), with both usually carried slung on the back leaving all four limbs free to climb and run.  Their prehensile tail carries the deadly Thch-Tock, the obsidian disc thrower or the tail sword.  Body armor us usually avoided as mobility is prized over protection.  Though in a war, leather armor is known, to include a light leather sleeve for the tail. 
 
Some more primitive tribes, or tribes that stay with traditional methods or otherwise want to avoid outside influences may still use painstakingly carved warclubs edged with obsidian as an edge. 
 
The lizardman naturally blends into the desert terrain and is well practiced in using that advantage. An attack will usually consist of a sudden series of whiplike snaps followed immediately by the impact of obsidian throwing discs slashing into the surprised defenders and howling warrior's boiling out of nooks and crannies to overrun their enemies.
 
If surprised themselves, they will generally simply scatter in all directions trusting that any pursuers will not be able to scale the terrain as easily or quickly as they can. 
 
Any "columns" that dare enter their territory will also be constantly harassed by warriors flinging obsidian discs and immediately repositioning. 
 
 
 
 
 

Something that is made from a smallish turtle-like shell, roughly about the size of a small buckler. But it is attached to the back of the hand/wrist of the user. 
When the user's hand is closed in a fist, the front edge of the shell ends up being 3-4" beyond the end of his/her fist. They attack by punching/stabbing with the front edge of the weapon/shell. 
This edge is either blunt (for training purposes, religious beliefs or non-lethal combat) or sharpened into a fine edge, doing KA damage. The richer the user and/or better the craftmanship of the weapon might might include sharp obsidian inserted into the edge causing more damage. 
The shell weapon can also be used to block attacks, stops venomous spit attacks from some of the dangerous reptiles, and the like. It is also a cultural tool, used as a scoop for quick digging in the sand to quickly build small shelters from the frequent sandstorms or to dig up small sources of water or plant roots. 
The back of the shell (or type of shell used) can be painted with symbols to differentiate different tribes, groups, religions, social status and so on. 

Just a note on Sean's PRE Attack example. Even if the GM allows a PRE Attack to use Haymaker (questionable in my opinion) that would negate several of your complaints about PRE Attacks. The Haymaker Maneuver takes a Half Phase Action (one might even argue it would be considered an Attack Action ending your turn) and the PRE Attack wouldn't effect anyone until the end of the next Segment. If a villain really wants to pose and posture at -5 DCV potentially leaving himself open to multiple attacks that could disrupt the PRE Attack from even happening, well, okay? My point is mentioning Haymaker in your analysis seems not well reasoned.
Applying Push is also highly questionable in my opinion. 
You point out that PRE Attacks can take place out of turn sequence, but then give examples that require them to be taken during your turn to get bonuses from your actions. You complain they are instantaneous but then apply Haymaker which would make it not so.
You complain there is "no reason" for every character to not "pop off" a PRE Attack the first round of combat even though repeated PRE Attacks suffer penalties.
 
None of these points in themselves negate your concern of 60 points worth of PRE being superior to 60 points of Blast, but your comparison would look more intellectually honest without inflating your numbers in those ways and acknowledging the penalties involved as openly as you acknowledge all the bonuses you award yourself.

we DO have a creepy images thread

The "PRE Attack Problem" is not fundamentally different form the "Blast Problem," which is that if the player characters are built to take 12d6 Normal Attacks and I hit them with a 25d6 Blast, I will wreck them. "Well, don't do it then" is in fact the perfect solution to the Blast Problem, and is also the perfect solution to the "PRE Attack Problem"
 
And we might as well ask about the rules for the Power Blast, "If we are never going to use it (defining "use it" as "wreck the player characters with an overwhelming Blast they're not built to handle)" then why have it?"
 
We have it because it's a good and useful Power. We have PRE because it is a good and useful Characteristic.
 
Just in case we'd like to , you know, play Hero System in a fun and reasonable way.
 
Lucius Alexander
 
I could unleash a Killer Palindromedary on the player characters, but why would I do that?

Does it matter?  GMs have an infinite point budget.  I'll just write "Meteor Bonus" under its Discomplivantationages.  
 
 
I do use it.  I use it on PCs, occasionally, even.  I don't hit them with 20d6 PRE attacks, though, any more than I'd hit them with a 20d6 Energy Blast, out of the blue, or put them up against a 100 STR brick.  
 
But sometimes, you do have a brick character get hit by a truck, just to show how tough he is.  I think that in this case, a high PRE attack can certainly do that as well.  
 
 

If that's how you habitually use PREsence attacks, no wonder your players don't like them.
 
If their only exposure to Martial Arts were guys who outclass their Combat Values by 4 or 5, and stun with every hit, they wouldn't like Martial Arts either.
 
Lucius Alexander
 
If every time I put a palindromedary in a tagline I hit you over the head with it, you probably wouldn't like palindromedaries either
 
 

Charisma was part of D&D from the beginning. And the wargames that the first role playing games evolved from had morale mechanics.
 
This is neither something unique to Hero, nor a Hero innovation. We're talking about a kind of mechanic that not only predates Hero System, it PREDATES ROLE PLAYING GAMES.
 
Lucius Alexander
 
and a palindromedary providing morale support

I have yet to have a player say, "Hey, I paid points for [thing] but it's never come into play."  Then again, I also haven't ever had a player complain, "I got points for [Complication] but it's never come into play." 
 
As GM I do try to work in various odd bits that characters have paid for.  (For example, Circe the mentalist has KS: Fashion, so I had her interact with a supervillain - who worked as a male model before getting his powers - having a relatively long discussion about superhero / supervillain fashions in the middle of a fight, rather than actually, y'know, fighting.)
 
Sometimes, it's up to the player to find ways to use the things he paid for.  If a character has Bureaucratics and the team is investigating an office building they suspect is owned by VIPER, there's nothing stopping that hero from going down to City Hall and finding a way to get the building's blueprints, or tracking down the building's ownership, or whatever else might be useful.

http://www.killershrike.com/GeneralHero/BellCurve.aspx
 
 
I encourage you to please consider clicking the links for consistency and distribution and bone up on the subjects a bit, it probably won't kill you and it might even benefit you.
 
 
-2 is what I'm suggesting, actually. But that's irrelevant to the flaw in your logic here. Allow me to break it down.
 
In your scenario the attacker has a +4 net bonus over the target at full DCV. No amount of penalty to DCV will make much of a difference on a 3D6 curve when the before-penalty difference is 4 steps or more away from mean. That would be classed in the category of "working as intended". 
 
So lets instead try an example made of less straw.  
 
Captain A normally has a 12 DCV but is currently stunned. As written, Captain A drops to 6 DCV, suffering a -6 DCV penalty. As suggested Captain A drops to 10 DCV, suffering a -2 penalty. 
 
Also in the scene is Doctor Stranko who is normally 10 DCV, but is Concentrating to cast a spell. As written, he drops to 5 DCV, suffering a -5 DCV penalty. As suggested, Dr. S instead drops to 8 DCV suffering a flat -2 penalty.
 
Professor Ex is there with his 12 OCV. If he were to target staggered Captain A, as suggested he'd hit ~84% of the time vs 99.5% of the time as written. If he were to target concentrated Dr. S he'd hit 95.4% vs a 99.5% as written.
 
So breaking this down finely:
 
You seem to be under the impression that "consistent" refers to the differences between percentages at each step in the distribution. It does not.  An equation system is inconsistent if there is no set of values for the unknowns that satisfies all of the equations; and is consistent if the opposite is true. In this case the wildcard nature of 1/2 DCV resulting in a different value for the same situation (1/2 DCV) is not consistent. 
 
p = DCV penalty
 
If p is a fixed value, then the following could be written and would be true where p=2
 
C1(11 + 12) - (12-p) = 13-
C2(11 + 12) - (10-p) = 15-
 
12-10 = 15-13
 
This could be reexpressed as the more general function which is consistent for any fixed value of p.
 
C1(11 + x) - (y-p) = r1-
C2(11 + x) - (z-p) = r2-
 
where y>=z
y-z = r2-r1
 
You can then test that by plugging in whatever positive values you like and you should find that it is always consistent when p is a specific fixed value and is not consistent when p is indeterminate due to being based on a halving of some other variable and which may be a different value per character. Further statements could be made from there.

As an aside, removal of the multiplicative aspect of 1/2 DCV also simplifies the order of operations and would allow the notation to tighten up a bit and also allow them to be applied in any order:
 
C1(11 + x - y - p) = r1-
etc
 
But that's not relevant / doesn't change anything for purposes of this discussion per se. The main takeaway is that the value of the penalty itself as a fixed number is consistent (the value of the penalty itself is consistent in the colloquial sense and it is possible to formulate mathematically consistent expressions around it) vs the value of the penalty as a fraction of some other number (the value of the penalty is not consistent colloquially; it may or may not be consistent mathematically speaking...feel free to work it out if you are motivated to do so).
 
 
You also seem to be under the impression that the way to assess impact on a Gaussian curve is to do so at the edges. It isn't. The greatest impact is by definition closest to the mean. That is in fact the core concept. To assess the impact one looks most closely around the mean. I.e., on a 3D6 / 3-18 / 16 step curve between +/-1 to +/-4, with +/-3 being the point of collapsing probabilities. Ever wonder why 8- and 14- are "special" / show up in various contexts in the HS? That's why.
 
CV's from 4 to 5 (or +1 to +2 over baseline) would not be significantly affected by a change to -2 vs 1/2 DCV. It starts to matter a bit more around CV 6 (+3 over baseline), and then every 2 steps beyond that matter.
 
Similarly, if the attacker's OCV is more than 3 steps (+4 or better) beyond the defender's DCV before penalties, then the DCV penalty itself is so close to being irrelevant as to not matter as the attacker is already out on the edge of the distribution curve and are meant to be there. 
 
 
As we are talking about a 1/2 DCV penalty vs a -2 DCV penalty the difference to be compared is that between the two penalties, and at different values of DCV. So poor Agent #3 is going to be busy attacking three different opponents at different DCV's calculated for 1/2 DCV and -2 DCV.
 
vs DCV 8 Guy example:
RAW 1/2 DCV penalty:  OCV 6 vs DCV 4: 13- / 83.8% == +46.3% diff
flat -2 penalty:                 OCV 6 vs DCV 6: 11- / 62.5% ==  +25% diff
 
As we are talking about the idea that two different characters with different DCV's being affected in a more consistent way by taking an action that is currently 1/2 DCV you also have to plug in a second target to compare and contrast. Thus:
 
vs DCV 6 Guy example:
RAW 1/2 DCV penalty:  OCV 6 vs DCV 3: 14- / 90.7% == +28.8% diff
flat -2 penalty:                 OCV 6 vs DCV 4: 13- / 83.8% ==  +21.3% diff
 
What we see here is the 1/2 DCV version swinging wildly even at a small difference in base DCV (17.5% jump from DCV 6 to DCV 7), while the flat -2 results does not exhibit that behavior relative to itself or its progression.
 
We can further show that by stepping up.
 
vs DCV 10 Guy example:
RAW 1/2 DCV penalty:  OCV 6 vs DCV 5: 12- / 74.1% == +57.9% diff
flat -2 penalty:                 OCV 6 vs DCV 8: 9- / 37.5% ==  +21.3% diff
 
 
Again, you are misusing the term "consistent" when what you are talking about is probability density / different relative likelihoods along the steps of a normalized distribution curve. 
 
To summarize your argument: You seem to think I don't know that the step from say 11- to 12- represents a greater probability density than say the step from 14- to 15-. I assure you I am fully aware of this. You seem to think that the term "consistent" refers to the %-ile values across the steps of the curve. It doesn't. You seem to think that if there is minuscule difference at the edges of the curve between the two methods (which of course there is because that is how normalized distribution curves work) it means the flat penalty offers no benefit over the 1/2 DCV version. This is incorrect; the impact is felt towards the middle of the curve (which of course it would be because that is how normalized distribution curves work).

I'd have to artificially insert something into a campaign that otherwise wouldn't have such items and the characters who sold off their MOCV would all turn to the mage and bard in the party who have actually raised their MOCVs and just hand it over.
 
There would be zero inconvenience unless I further contrived an encounter where the bard & mage get - say Webbed - where their spell casting is shut down and their low STR scores prevent them from escaping and then follow it up with making such an item only be within reach of the characters who sold it off and.. barf...  it would be so obvious I was targeting the character for the sell off that it would likely irritate the player.
 
And while I wouldn't characterize myself as lazy I do have a full time job and a family so the two tables a week I run are based on ready made campaigns (one Pathfinder the other D&D) that I convert on the fly.  I may sprinkle in some ad lib material here and there, but I lack the time for a fully home built campaign.
 
 

A bell curve has nothing to do with mathematical consistency one way or the other. You are confusing consistency with distribution. Each step up or down (or left to right, depending on your visualization) along the standard normal distribution has a potentially differing probability density / i.e. is of different relative likelihood and are thus not of a constant value but that is not what consistency refers to in the context of mathematics. 
 
If Character A and Character B attempt the same action and suffer the same bonus or penalty value, it is consistent and also the guassian curve / standard normal distribution applies. 
 
But if Character A and Character B attempt the same action and suffer a different bonus or penalty to each other, then that is inconsistent, and the bell curve doesn't PREVENT that inconsistency...though it does MEASURE the inconsistency relative to the normal distribution. 
 
In other words, if Character A and Character B both take the same 1/2 DCV action, and Character A suffers a -3 penalty for doing so while Character B suffers a -1 penalty for doing so, a bell curve does not prevent that and nor does it somehow make that "consistent".
 
Lets have some fun with numbers...
 
3d6 Bell Curve            3d6      Pct           Odds      3 0.5% 215 : 1 4 1.9% 53 : 1 5 4.6% 20.6 : 1 6 9.3% 9.8 : 1 7 16.2% 5.2 : 1 8 25.9% 2.9 : 1 9 37.5% 1.7 : 1 10 50.0% 1 : 1 11 62.5% 1 : 1.7 12 74.1% 1 : 2.9 13 83.8% 1 : 5.2 14 90.7% 1 : 9.8 15 95.4% 1 : 20.6 16 98.1% 1 : 53 17 99.5% 1 : 215 18 100% 1 : inf  
Characters A & B.
 
Character A has 6 DCV, Character B has 3 DCV.
 
Character A takes a 1/2 DCV action and drops to 3 DCV. 
 
Character B takes a 1/2 DCV action and drops to 2 DCV.
 
Assuming a neutral 11- 62.5% to hit, Character A suffers 21.3% of probability protection vs getting hit while Character B only suffers 11.6%...in other words, on neutral odds Character B is basically half as impacted as the character who paid for twice as much DCV. This is inconsistent between the two characters (they are affected in a disproportionate way, in real numbers), and further is also inconsistent to the system's meta concept of "pay more points to get more benefit" in that the character that paid more to be good at not getting hit suffers a bigger penalty when using the 1/2 DCV action. Thus there is an entire category of abilities and situations (those resulting in 1/2 DCV) that are biased against the character that spent points to raise their DCV and are biased towards the character that did not. 
 
If the action imposed a flat -2 DCV rather than 1/2 DCV, then Character A drops to DCV 4 and Character B drops to DCV 1. That works out to a 11.6% loss for Character A and a 12.5% loss for Character B. The character who paid less is affected slightly more, which better befits "get what you pay for", and the difference between the two outcomes is much closer. The range is smaller, the variance is less, the impact is linear, the penalty value is the same (-2 vs -?), and thus it produces results that are both more consistent and more normative.
 
It doesn't matter which values you plug in, as long as you avoid break points. Every 2 steps of DCV results in a deepening of the impact.
 
Put a different way. A 1/2 DCV maneuver is a -1 DCV penalty maneuver for DCV 3 Guy and a -3 DCV penalty maneuver for DCV 6 Guy...for no viable reason. This is particularly odd in that penalties in the Hero System are generally used as consistent negative modifiers for the purposes of reducing % chance of success to represent the relative difficulty of whatever is being attempted by a character. They are not relative to the character attempting the task, they are fixed per the task being attempted. For example, modifiers based upon relative ease of a given task are:
 

 
Thus, a character with 12 DCV taking a 1/2 DCV action is the equivalent of a "Sheer Folly" difficulty (-6), while for the character with 3 DCV to take the same action its the equivalent of a "Difficult" difficulty (-1). This doesn't make logical sense to me, as the two characters are attempting the same action.
 
But I hear you say "well, those are task modifiers, dummy. DCV penalties are different" (somehow , even though a 3D6 roll under attack and a 3D6 roll under skill are actually on the same curve, but whatever).
 
Uh huh. Ok, how about this then?  Poor footing is a -1 DCV. If it is also on a tight rope that's another -2 DCV. So, a character fighting on an oil slicked tightrope takes a flat -3 DCV, while a 8 DCV character taking a 1/2 DCV action such as Bracing suffers a -4 DCV. That may make sense to you, but it does not make sense to me.
 
IMO, if a find & replace were done across the rulebooks to change all references to 1/2 DCV to instead be a flat -2 DCV it would remove that sort of nonsense (similarly, though much less commonly a thing, 1/2 OCV to -2 OCV). There's some logical follow through permutations to that, but I'll punt on exploring them right now as I have other things to get to tonight.

Is Steve's answer a change that has been made in the official errata? Because that is not how the Invisibility power is described in 6th Edition rule book. Like others have said the main points in the rules are: 
 
 
And "below" in the power description the only other reference to Foci (apart from using weapons to attack) is:
 
 
So by the rules of 6th Ed, as written in the book, Foci are covered by Invisibility unless it is an Obvious Foci that is generating the Invisibility power, or if a Foci is being used to attack someone, in which case it appears on the segment the attack is made, then turns invisible again.  That means all other Foci, Obvious or Inobvious, turn invisible when the power is used and stay that way unless used to attack.
 
There is really no other way to interpret the rules as they are written. It is very specific in the book that all Foci, Obvious or not, are covered by the Invisibility power unless it is an Obvious Focus creating the power. 
 
So Steve's current answer has to be a change to the rules that should be addressed in the official errata (and maybe it is, I haven't read through the errata).

If you watch them turn invisible, it will be obvious that the focus is doing it. if you see someone as they appear from Invisibility, you can also tell the focus is responsible
 
If you can see the fringe effect you can also see the foucs and can tell it is causing the invisibility
 

Invisibility to the hearing sense group would still cover the ring. No one has argued invisibility to sight would stop a sound, you using that as an example in the first place is a complete non sequitur from the topic.
You state:
"Invisibility doesn't make the SFX of your powers stop being obvious so the SFX of "ring is obvious because it shoots tinymagical shields" remains obvious.  Again, Darkness construct."
Well, per the rules the SFX of a mundane weapon like a sword  is that it is an Obvious Focus of a Power. You are arbitrarily granting some SFX a bonus over others, regardless of your attempts to justify it.
Also, nowhere in the rules does it state that the Images Power produces light (unless you are specifically building a light power). Claiming the "light escapes Invisibility" is a nonsense arguement based on your idea of certain SFX and had nothing to do with the rules of the game or how Powers are actually described as working.
EDIT: Also, claiming someone with a Distinctive Feature can't be turned Invisible is just crazy to me. I don't even know how to approach that. By your own standard someone with the Distinctive Feature:  "12 foot Lizardman", Not Concealable (no Ninja Turtles trench coat is going to hide this guy) could not be turned Invisible.
 

Invisibility to the hearing sense group would still cover the ring. No one has argued invisibility to sight would stop a sound, you using that as an example in the first place is a complete non sequitur from the topic.
You state:
"Invisibility doesn't make the SFX of your powers stop being obvious so the SFX of "ring is obvious because it shoots tinymagical shields" remains obvious.  Again, Darkness construct."
Well, per the rules the SFX of a mundane weapon like a sword  is that it is an Obvious Focus of a Power. You are arbitrarily granting some SFX a bonus over others, regardless of your attempts to justify it.
Also, nowhere in the rules does it state that the Images Power produces light (unless you are specifically building a light power). Claiming the "light escapes Invisibility" is a nonsense arguement based on your idea of certain SFX and had nothing to do with the rules of the game or how Powers are actually described as working.
EDIT: Also, claiming someone with a Distinctive Feature can't be turned Invisible is just crazy to me. I don't even know how to approach that. By your own standard someone with the Distinctive Feature:  "12 foot Lizardman", Not Concealable (no Ninja Turtles trench coat is going to hide this guy) could not be turned Invisible.
 

Of course, the monster I'd most like to be is a dragon.  However, I'm not really greedy and all dragons are greedy.  
 
So, I'm somewhat slow and methodical, I stay confined to a set area, I'm generally open and honest which leads to a lot of transparency in my life, the people closest to me often say I'm amazingly silent and sneaky for my size, and I've collected a rather large, odd assortment of weapons throughout my life.  The monster I'm probably closest to is: 
 
Gelatinous Cube