Lifeblood is a dlc for hollow knight and is the third out of the four free contents that were released. This dlc was announced on the 23rd of march 2018 and was released on the 20th of april, 2018. Lifeblood mainly focused on enhancing certain aspects of the game such as: Lifeblood core in hollow knight is one out of the 45 charms that is found in the game. These charms are special items that provide the knight buffs that will help with both traversing hallownest and battling its foes. Charms require notches and can only be equipped and unequipped while having the knight sit on a bench. Lifeblood is one of the few aspects of hollow knight that remains shrouded in mystery even now, four years after the game was released. The glowing, blue substance seems to have some signs of sentience, evidenced by the existence of the lifeseeds and another possible creature.