Nullstone

Nullstone costs 3 at Sho'guul's lair.

It blocks one attack per room and reappears when the player enters a new room. It negates almost all types of damage (including from Sacrifice Rooms and Purge Potions), except Mortar's beam attack and fire damage from landing on a torch. Blocking hits prevents status effects from afflicting the player (e.g., a Spider's poisonous bite or projectiles from Waking Light-affected Torches and wall lanterns). Blocking a hit prevents the Intensifier's effect from resetting.

The Nullstone activates after, and.

When the Nullstone disappears any s on the player will be removed.

Tips
Because the nullstone blocks damage taken from buying items with health (for example blood offering), it can easily be used to clear out shops with no cost. You can buy an item, enter a new room, go back and buy another item, and repeat this process.