Memento Mori

Memento Mori, remember to die, is a concept created by the gods to remember mortals of the mortality.

History of term
Memento mori started as a way for the gods to control mortals, saying that "they who cannot die" had the right to be worshipped by the "ones who do so", but turned into the symbol of their own mortality and equalty between them and mortals. The change of meaning happened after the first godslayer killed the god Cronus with a technique named posse perire deos (gods can die). After the god's demise, the godslayer used his last strength to yell the words memento mori and eventually fell dead because of the wounds of the fight. Many gods saw their mistake on underestimating mortals and "gave up godhood".