|"We must've been through hundreds of books already and we can't find him anywhere —"|
Mortality is the state of being mortal, or susceptible to death; it is the opposite of immortality. Almost all known beasts and beings, both magical and non-magical alike, are subject to mortality. Spirits, however, are not, as they have either already died or were never truly alive.
Phoenixes are the only living creatures known to be naturally immortal, as they are immediately reborn from their ashes after dying. Other methods may be used to grant immortality, such as Horcruxes and the Elixir of Life, although such sources may be withheld or destroyed, rendering their user mortal once again.