Selene

At 17,000 years old, Selene is by all accounts the oldest mutant in the Marvel Universe, older even than Apocalypse.

Selene was "old when the world was in its infancy." Born in central Europe after the destruction of Atlantis, Selene already existed before written word, during the Hyborian Age, when she rubbed elbows with Kulan Gath and Conan the Barbarian no less. She was even worshiped as a goddess in some places, suggesting she could be her namesake in Greek mythology.

Yet in all these years, Selene has never gone long without obliterating her wrinkles. Incredibly vain, she has used her power of draining life forces to rejuvenate her appearance across the decades. While her victims crumble to dust, she becomes sexier and comelier than women a fraction of her age, let alone anyone reliant on botox, facelifts and fillers.

Selene ambles through the millennia on the lookout for ways to increase her power and maintain her youth. Like any aged vampire, Selene is one very bored woman. At one point, she imagined herself longing to relive the glory days of ancient Rome. She then fabricated an 'ancient' city-state, Nova Roma, in the Amazon forest. Later she found herself in New York City, jointly leading the Hellfire Club as its Black Queen. 

One of only three remaining Externals—she killed most of the others—Selene has an incredible arsenal of mutant powers, to say nothing of her masterful knowledge of witchery. For all her endowments however, Selene has always yearned to become a bona fide god. It is this motivation that forms the crux of Necrosha, a 2009-2010 story arc that pitted many Marvel heroes against Selene.