Omega-level mutant
In the Marvel Comics Universe, a mutant with the ability (or potental) to exist beyond the physical realm and consciously explore the metaphysical. Immortality is also a possibility but not a requirerment.
Omega speaks for potential. X-men forever spoke of how humanity sees the result of experiments the Celestials carried out on early lifeforms, on behalf of the abstracts entities of the Marvel Universe (Eternity, Death, and so forth). The reason for these experiments was to ensure that a race of beings would eventually evolve that would surpass and in turn replace all of the aAbstracts. This would bring about the end of universe. By creating humanity the abstracts are ensuring that the cycle of life continues to revolve. This final state of evolution is phoenix. Its what all humanity will eventually turn into. Thats why Jean as phoenix is called the "ultimate mutation". Those with omega (the last) potential are the ones closest to reaching this final stage of evolution. Whether their potential results in they themselves turning into phoenixes (like Jean and Quentin Quire have) or their descendants doing so, within Omega-level mutants lies the potential to bring about the end. Hence its name.
A list of confirmed Omega Level Mutants:
Possible Omega Mutants (based on demonstrated abilities and power levels)
- X-Man
- 'Jesus' Cable
- New Sun (Gambit)
- Franklin Richards
- Hyperstorm
- Marvel Girl Rachel Grey