Crystal Heart

Crystal Hearts are objects found on any layer below the surface. When the player breaks a Crystal Heart using a Hammer, or explosives, it drops a Life Crystal which can be picked up. The life crystal can be used to increase your maximum health by 1 heart (or 20 HP). It also heals you by the same amount.

It should be noted that crystal hearts can be easily found in the Dungeon, or in The Underworld