Another aspect of Dark Souls is the "humanity" system. There are two "forms" the player character can be in during the game, human form and hollow form. Whenever the player dies in human form, they are returned to hollow form and can only have their humanity restored by consuming an item (also called a "humanity"). In order to gain the assistance of other players, the player must be in human form. While in human form, the player is subjected to invasions by other players and non-player characters (NPC) who seek to kill the player and restore their own humanity. Humanity can be acquired in many ways, and if no humanity is available, players are still able to progress in hollow form. Death in either form results in the loss of all carried souls and humanity, but players revive as hollows at their most recent bonfire with one chance at returning to where they died to recover all lost souls and humanity. If the player dies before reaching their "bloodstain", the souls and humanity they previously accrued are permanently lost.