The Alien alliance which invaded the earth in 1989 consisted of a large number of species, but six are particularly numerous: -
Dominators are tall thin yellow skilled humanoids with grille-like mouths. They are the leaders of the Alliance and make up most of the Scientists and administrators. They live in a Caste system with each individual having a red disk on their forehead, the larger the disk the more important the Dominator.
Khunds are large yellow skinned Ogre-like creatures. They are extremely aggressive and make up the majority of the alliances military forces.
The least humanoid of the common aliens. The Gil'dishpan appear as a blob of tissue in a grass dome which contains a liquid medium. The Gil-dishpan possess strong psychic powers and are capable of telekinesis and mind control. They seem to have a unrelenting hatred of humanity.
Daxamites appear human from the outside. They are the most powerful of the known aliens showing enormous strength and toughness as well as flight, super speed and heat vision. They were responsible for the death of Superman. They are rarely seen on Earth.
Thangarians are near indistinguishable from humans from the outside although their internal systems are significantly different. Thangarians act as light infantry and a police force to the Aliens, they often use large wing like devices to fly with.
The Durlans are a race of shapeshifters. Their natural appearance is normally covered with thick robes from which tentacles often protrude. They are natural spies and infiltrators.