Nihil had an insectoid face and leathery bat wings (one of which was torn off), and though four-limbed like a human, both upper limbs divided at the equivalent of his elbows into two lower arms and hands, each hand possessing two talons and an opposing claw. Nihil was an extra-dimensional alien, with completely non-human internal organ structures.
Annihilus is the tyrannical ruler of the N-Zone. The members of his space-born race are exceedingly long lived, and Nihil could live long after the N-Zone universe has died. As Nihil's solar system has aged, he has slowly gathered the vessels of whatever life forms he found, melding their ships into one large conglomerated station, also apparently claiming whatever he needed from those he saved. In this manner, he built himself a large kingdom, a space station in which he took what he wanted while returning the necessities of life to his vessels. The name "Nihil" is actually a traditional cast title for leaders and punishers, dating back to feudal times of his race.
When the Fantastic Four visited the N-Zone, Nihil detected them and sent out a hailing beacon to attract their attention. After the foursome's translation techniques proved ineffective, translating Nihil's name as "Annihil Us", Nihil provided them with his own translation devices (which, unbeknownst to the Fantastic Four, contained explosive devices). Collecting information on their home system, Nihil determined they were from a parallel dimension which was younger and had a much longer prospective lifespan. The discussion was curtailed when Johnny Storm took ill and the four decided to leave. When Reed Richards and Ben Grimm informed Nihil of this, he decided to kill them both and take their ship for himself. Despite destroying their suits integrities by detonating the translating devices he had attached to their helmets, Nihil was defeated in hand-to-hand combat by Ben, who managed to tear off one of Nihil's wings during the fight. While his vassals delayed Reed and Ben's escape, Nihil got to a ship and pursued the Fantastic Four to their home dimension. Both ships crashed on the Sunset Strip in Las Vegas, and while the four defeated his servants, Nihil himself was apparently killed by one of his own weapons while battling Mister Fantastic, when Reed exploded Nihil's head. The lasting affect of this battle is that the Fantastic Four's secrecy was blown and the team had to be given a formal introduction to the world.
Nihil could fly and possessed very sharp talons. He could survive in various atmospheres toxic to humans, as well as in Earth's atmosphere. He was immensaly old, with a life expectancy of more than one million years ahead of him.
Though not a scientific genius, Nihil has accumulated untold years of scientific knowledge.
Nihil had access to tecnologies from hundreds of alien races, including translation devices, weaponry, and space ships. As feudal ruler of his ship and surronding areas, Nihil controled and demanded the service of those on his ship, willing it or not.