Stick it in the ground and it's a makeshift bonfire.
Spawn a Bonfire at the Boss Stage path. (Artifact must be equipped when entering preparation room) Interacting with the Bonfire fully recovers HP.
Once per boss, the player character will respawn back at the preparation room after death (Artifact must remain equipped during the boss fight)
Defeat Chapter 3 Mid-Boss Eldrich (CH03 Mid-Boss) 2 times without taking damage from Eldrich's Skeleton Swordsman.