Key Items are collectible objects that are generally used to open special doors or solve puzzles, and are generally finite in number. The only exception to this is the Proud Soul, which is rewarded after every mission in Devil May Cry 4, and replaces Red Orbs as the currency used to purchase new abilities. Certain Key Items can also drain the player's health, forcing them to use the item before they expire. It is impossible to keep Key Items in the inventory throughout missions, as they operate as plot items. While this is still true in Devil May Cry 4, the abilities that a Key Item grants can be used regardless of whether the player still possesses the Key Item or not.