Heart of the New World
Type: Unique Artifact
Pay 5, you may only do this once per turn: Target character can only be killed by combat damage until the end of turn.
At the end of turn, if you control no deployed characters, sacrifice Heart of the New World.
All characters that died or were removed from game this turn are resurrected/brought back to your support zone. Heart of the New World is removed from the game.
"A mysterious relic from the previous inhabitants of the New World. Though incomplete, it is the only reason that there is still life to be found. Would it have been completed sooner, Aleta might not be the only of her kind today." - Prophet Karani
I think it is pretty obvious what the Heart is meant to do. I just wanted to point out that it brings back all characters, including your opponents. So it is not an easy 2 card win combo with calamity.
Also, characters protected by it can still take damage from spells, they just cant be killed by them (so they will survive any damage spell with at least 1 hp. Insta-kill spells will do nothing though).