Nirkana Cutthroat

Effects that set a leveler’s power or toughness to a specific value, including the effects from a level symbol’s ability, apply in timestamp order. The timestamp of each level symbol’s ability is the same as the timestamp of the leveler itself, regardless of when the most recent level counter was put on it.

The abilities a leveler grants to itself don’t overwrite any other abilities it may have. In particular, they don’t overwrite the creature’s level up ability; it always has that.

A creature’s level is based on how many level counters it has on it, not how many times its level up ability has been activated or has resolved. If a leveler gets level counters due to some other effect (such as Clockspinning) or loses level counters for some reason (such as Vampire Hexmage), its level is changed accordingly.