It (it's beyond questions like gender) often looks like an aryan man in his early 30s, always dressed with white clothes. Physically he's like a smoke-like illusion, partially vanishing in the air. It maintains this last characteristic in all forms, independently of shape, texture...
Unknown. At some point of it's life took the name of a human called Evan Halls for no aparent reason, making that man dissapear from almost all realities; now the fact of that the original Evan existed is only known by some Omnipresence users.
As an entity of residual psionic energy Evan has powerful psychic powers:
Psycho Warping: This mysterious being is able to change reality using his huge amount of psychic power. It's so powerful that can overwhelm almost all normal psionics.
Nonexistence: Because a part of it was made by pure nothingness it's able to combine his psychic abilities with this inexistent component, reaching a God-like power based on anihilation.
Freedom: Even if Evan has this ability anyone knows if it also has his own will and desires.
Psychic Power Negation: When attacked with psychic or psionic powers it'll just "eat" that energy.
Psychic Energy Physiology: Evan Halls is completely made of residual psychic energy.
None. It's always apathic, standing completely still. Some power users that saw it say that's mumbling it's own name again and again there... in the middle of nothingness...
The great weakness
If the opponent is a powerful enough psychic user they would be able to manipulate Evan Halls at will,since it's entirely made of psychic energy.