I like the idea of immortal Immortals
. I think their name doesn't mean "untargetable", but "undying". Other thing is with Phase Dragons as (just my imagination) they phase out for a second, so they can't be targeted. How about changing Immortal stats, removing quint and giving him passive skill "Immortal", which means "When killed, becomes Immortal again". That wouldn't make any problems with gravity pull combo or Rage Potion, but would be cool:
Creature against CC
Cremation fodder (even now, when it's nerfed)
Devour fodder
That would be also cool, cause it could be stopped by freezing, but also buffed by your spells.
Just an example of such card:
Immortal 4/3 for 4 quanta, immortal -------> Elite Immortal 5/3 for 5 quanta.
It's quite cheap, so it wouldn't be only in Aetherstalls, and can be stopped by delaying and freezing so it isn't OP to give them Attk equal to cost.
How about that?