Charm of Life
The Charm of Life is a small, heart-shaped item found as treasure. When a player carrying one of these charms would normally take lethal damage, the charm will activate, preventing the damage, healing the player, and consuming the charm.
The charm comes in two varieties. The Charm of Life I will heal the player back to 4 hearts, and bestow a weak regeneration effect for the next 10 seconds. The Charm of Life II will heal the player fully, and activate several powerful regeneration and protection effects for the next 30 seconds.