Re: Understanding Drow Creation
Actually applying the linked limitation like that is explicitly denied (Unless the GM permits it). You cannot link an identical power to another to form a larger one.
There's a difference between energy blast 2d6 plus energy blast 2d6 (only vs evil -1/2) (linked -1/2)
and
Energy Blast 2d6 plus Energy Blast +2d6 (only versus evil -1/2)
The former version fires two seperate 2d6 blasts and enemies would apply their defenses seperately against both. So if an enemy has 7 PD he would apply each 2d6 against it seperately, and probably not get injured much.
The Latter is the correct way to build the power as the second energy blast is being defined as adding to the first. Forming a power that does 4d6, but only if the enemy is evil, doing only 2d6 if they were not. They will apply their defenses once to the whole 4d6 damage. You cannot apply linked to the second energy blast because it is already being built to explicitly add to the first.
That being said your power also needs to have area of effect for what you are describing. Depending on the radius you want you should either take area of effect (one hex) or area of effect (+1 per 1") and double it until you get the desired area. This does however run into a problem since I'm unsure of how the area is affected by the powers being added together. That would be up to the GM unless someone knows the actual ruling.
Here's how I would have my players build it. I would give them the benefit of doubt and say it covers the full area of 2" despite it being two seperate 1" radii, combining the active points of the two to determine it's actual radius. (See page 247 5th ed. rev. for area of effect)
Energy Blast 2d6, Area of Effect(+1) plus Energy Blast +2d6, Area of Effect(+1), Only versus evil(-1/2) 40 active points, 33 Real points
10*(1+1) + 10*(1+1)/(1+1/2)
The cheaper way would be to keep it's area at 1 hex dropping the cost down to 25. Of course with a power as expensive as these you'll probably want to throw some additional limitations on it.
Alternatively I could see it being built using the limited power limitation. The power will lose half of it's effectiveness, about half of the time (being a bit generous there). So it's only losing about 1/4th it's actual effectiveness.
Energy blast 4d6, Area of Effect (+1) 40 active points; Loses half effectiveness versus evil (-1/4th) 32 real points
Edit: After thinking about it for a minute or two after posting, this limitation might not be worth any penalty at all, in fact, may be an advantage. It occured to me that you may be buying the limitation specifically to avoid hurting allies, making it more of an advantage, especially if you will be fighting primarily evil enemies. It's possible that I would not give any limitation for only doing full damage to evil at all, depending on those factors.