A Life Crystal is an item dropped after breaking a Heart Crystal. It is used to increase the amount of maximum Life the player has. When this item is consumed, it increases the player's maximum HP by 20HP (one heart) up to a maximum of 400HP (which requires 15 hearts). Additional Life Crystals collected can be used to make Heart Lanterns. To get higher amounts of health, one must collect Life Fruit in the Jungle.
Obtaining and using a Life Crystal is required to get the NurseNPC.
A common way to quickly get max life is to create multiple worlds to gather Life Crystals.
Life Crystals are more common in the underworld.
In the Alpha version of the game, Eye of Cthulhu used to drop a single Life Crystal on death. This has been changed in the Beta version.
If one somehow manage to attack a monster with a Life Crystal (use it while close to a monster) it will do 1 damage