Re: Champions Or Mutants & Masterminds?
I have both M&M 1e and 2e and pretty much every Hero book ever published (sad I know). The "true Invulnerability" question came up with me as well. In Hero the best way (I have found at least) is to use the Force Wall construct from Ultimate Brick. If you make it inherent and say, only good vs Fire or Cold, ect it is not that exspensive to get pretty much Invulnarable to something. Now you may violate some active point caps, if your campaign has them) so it will be up to your GM to approve it but I have never found it to be bad. You have to buy Indirect for you own powers to go thru (we usually just tack on another +1/4 to +1/2 advantage to let all your own abilities thru).
Even the 'Can't hurt me' power from Ultimate Brick made persistant is 55 Points. Anything doing 12 Body or less is stopped cold, seems pretty much just like the Impervious ability in M&M, almost identical in fact.
Invunlability to Fire-
Force Wall (0 Pd, 20 ED), 2" long (Sufficient to completely surround characters body), Reduced End (0 End, +1/2), Persistant (+1/2), Hardened (+1/4), Inherent (+1/4). (130 Active points):Always on (-0, not really disadvantage), No Range (-1/2),Self Only (-1/2), Restricted Shape (-1/4,Always surrounds character and conforms to his body), Only vs Fire (-1). Total Cost: 40 Points.
Now is he completely invulnerable?, No but he can ignore anything less than a 21 Body Fire attack, while I can't speak for anyone elses campaign that covers pretty much any Fire Damage in my campaign.