A Life Crystal is an item dropped after breaking a Heart Crystal. It is used to increase the amount of maximum Life you have. You must use either a hammer, hamaxe, Hamdrax or explosives to destroy the Heart Crystal and harvest the Life Crystal. When this item is consumed, it increases your maximum HP by 20HP (one heart) up to a maximum of 400HP (which requires 15 hearts). Skeletron has a chance to drop a Life Crystal. When you reach maximum life (400HP) they can no longer be used to gain more health, and can only be used for their sound effect and animation (that will not make the crystal disappear).