I understand where some people are coming from with the whole untargettable angle, but, (ignoring the code altering that would be needed to actually implement this card) how many cards use the immortal angle that this would prevent?
Light: Mirror Shield/Hope (both light shields)
Life: Emerald Shield
Air: NONE
Water: NONE
Gravity: NONE
Time: Anubis
Darkness: NONE
Death: NONE
Earth: Enchant Artifact
Fire: NONE
Entropy: NONE
Aether: Immortal/Phase Dragon/Quintessence
So out of all of the cards in the game, 8 have this ability, with 3 of them able to confer the ability onto other things. Personally, I think there should be a way to get rid of the untargettable ability, because with anubis, as long as he gets out first, there goes your opponents totally untargettable army coming and theres nothing you can do about it