Mortality, also called the New Dawn is the ultimate goal for most Prometheans. When a Promethean succeeds on their Pilgrimage, a change takes place; the Azoth powering the Promethean is replaced with a true soul, the Disquiet ends, their Transmutations disappear, and any benefits they get from maintaining an Athanor become part of their new form. Exactly how this happens is unknown; the only common factor is the methods vary wildly from individual to individual.
Prometheans who become mortal are pure human with no benefits, other than the lingering Athanor benefits. As a result, they are eligible for Embrace or the Awakening; if either happens, they lose their Athanoric benefits. It is also possible for a Promethean who has been gifted with Mortality to die, and have their corpse be remade into a new Promethean.