Wall of Bone

Creature — Skeleton Wall

Defender (This creature can't attack.) : Regenerate this creature. (The next time this creature would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

The Wall of Bone is said to be an aspect of the Great Wall in Hel, where the bones of all sinners wait for Ragnarok, when Hela will call them forth for the final battle.