Pure Coffin created blue gem-like isolated spaces which defied causality. Everything confined inside the spaces was cut off from cause and effect outside, similar to the Fūzetsu, which was yet to be invented in Asiz and Tis' time. The size and number of spaces created by Pure Coffin could be adjustable. Offensively, it could be used to imprison enemies or engulf and snap off a part of an enemy's body. It could also be used as a wall to protect the user.
When Tis used Pure Coffin during battle, her golden circlet Divine Vessel floated above her head and glowed like a halo and two pairs of wings appeared on her back. The spaces created by Tis were cube-shaped.
Directly after Tis' death, Asiz used Pure Coffin to preserve her body before materializing himself in this world. On top of its continued operation to preserve Tis, he used this power to kill many Flame Haze during his quest to find a method to revive her, and later, to grant her wish. The shape of the Pure Coffin used to preserve Tis was literally coffin-shaped.