The "grays" are by far the most commonly reported type of alien. Nearly all of the abduction phenomena involve reports of some variant of the gray type. A gray is about 4 ft. tall, has a comparatively large head and large, all black eyes. These are variously seen walking through walls, occupying UFO's, conducting various procedures on abducted humans, etc. These are said to engage in telepathic contact with abductees and to immobilize them either with some device or their stare. According to the Cassiopaean material, these are fourth density service to self beings created by the reptilian aliens to act as their robots or probes.
Also referred to as lizards, lizzies, or drachomonoids, this type is somewhat less frequently reported than the grays. They are described as 8 ft. tall, scaley beings that are like upright walking alligators with a vaguely humanoid face. These are said to control the gray aliens.
This type is relatively infrequently reported and looks like a Nordic human. These are said to be the higher echelon of the service to self hierarchy. Some beings of this type are also said to be of the service to others orientation; of the types listed here, this is the only one which includes fourth density STO beings, the others being essentially STS only.
In accounts of UFO abductions, human women are sometimes said to meet their half-alien hybrid offspring. The hybrids are various but look somewhere between a gray and a human, with large eyes and large head and no hair.
These are 12 ft. tall humanoid beings of third density that have been used as enforcers of fourth density service to self rule on Earth at various times in history. These have been rarely reported in UFO sightings or abductions. According to the Cassiopaea material, this type of alien will be again reintroduced to Earth. These are the giants referred to in the Bible, resulting from the intercourse of the angels with daughters of the Earth.
Some UFO abduction reports mention aliens resembling a praying mantis of human-like size.
By most accounts this is a large hairy being resembling a gorilla. According to the Cassiopaea material, these are not native to Earth and are used for menial tasks by fourth density STS.
The aliens are generally described as sexless or androgenous. Lizzies and nephilim are sometimes described as male. It is also said that there is no distinction of gender in 4th density and above. Hybrids are described as having both male and female variants.
Much literature exists concerning various types of aliens and the abduction phenomenon. The reader is referred to High Strangeness by Laura Knight-Jadczyk and to The Threat and other works by David M. Jacobs for more on this matter. As with UFO studies in general, the field is exceedingly fragmented and full of disinformation. There does, however, seem to be a bona fide abduction phenomenon as well as many consistent accounts of diverse alien types.