Zetan (Fallout)

Zetans are a species of Grey-like beings who have had many repeated run ins with the inhabitants of the irradiated wasteland which was once known as the United States of America, they have known of Earth and it's inhabitants since at least the 15th Century (possibly even longer) and have been abducting and experimenting on them ever since.

Biology
The Zetans are quite a variable in height and in appearance (one possibility is that the term Zetan is a term for several species who originate from the same star system/planet) but for simplicity's sake we shall call the taller ones which are seen in the Mothership Zeta expansion the 3-NV Zetans, and the more resent ones the the 4-76

The 4-76 Zetans are your typical Little Green Men-types with sharp teeth, three digits on each hand, spotted yellowish green skin and beady eyes, this type come in five varieties.

The type which reached the wasteland earliest was the standard type which have red spacesuits and use standard alien blasters.

The second type are known as Cryogenic aliens, as their name suggests this type use freezing weapons.

The third type are known as Toxic aliens, same as the previous type their name describes what their kind of weaponry, poisonous ammunition is at play with this type.

The fourth type is known as the Alien Invaders who have the same ammunition and weaponry as the first kind but they have heavier, more robotic armour.

The fifth type is much more mysterious, presumably they are some kind of first wave of attack or possibly some kind of scout before a full-on invasion, this type is notable as they are more commonly known as The Flatwoods Monster, this kind has the abilities of levitation, teleportation and inbuilt energy weapons.

Now as for the more lanky, scaly and scientific 3-NV Zetans, they usually stay confined to their Flying Saucers except for occasions where they send out small scouting parties to Earth, their hobbies include abducting human and performing experiments (including genetic splicing creating hideous Abominations) and interrogations on their abductees.

They have four digits on each hand two large nostrils and two large eyes with bumpy skin

History
The Zetans have been visiting Earth since at least the 15th Century as is evident by the fact that there was a bleepin' samurai onboard the Zetan Mothership.

The major pre-war governments of Earth first became aware of the Zetans presence during their timeline's space race, when the Orbital capsule Clarabella 7 (and it's pilot Colonel Hartigan) "disappeared" (meaning they where abducted by the Mothership) shortly after leaving Earth's atmosphere, the US covered up the abduction making up a silly excuse involving weather balloons, shortly after this the US Space Administration (the Fallout universe's version of NASA) launched the space station Valiant 1 into orbit as a means of observing or possibly even deterring the Zetan invasion.

Eventually the Zetans caused the station to fall back down to Earth following a global nuclear "exchange" allowing the Zetans to continue their operations well into the 22nd/23rd centuries

In 2103 a small 4-76 Zetan force was sent to Earth but where destroyed by the survivors of the nuclear holocaust along with another Zetan which was sent to the planet at an earlier date.

In 2277 a small Zetan scout ship crash landed in the wasteland and shortly after a human was abducted at the crash site, said human then proceeded to gather together the other human abductees and destroyed several Zetan ships.

In 2281 some more 3-NV Zetans landed safely near the New Vegas strip but where soon attacked by yet another survivor of the fiery baptism or Earth.

In 2287 another Zetan scout ship crashed in the wasteland and an injured 4-76 Zetan was present in a cave near the crash site, this being however was also killed by a survivor.