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 seemingly reptilian (or they just have a bad skin care routine ) they have three to four digits on each hand and have a binocular field of vision and they appear to be ether Oxygen or Nitrogen breathers as is displayed by their ability to breath Earth's atmosphere.

Their genetic code appears to be compatible with human genes (but it causes horrible Abominations)

They appear quite different across the Fallout franchise so for simplicity's sake we shall call the Zetans from the Mothership Zeta DLC the 3-NV Zetans and we shall call the ones who where seen more recently the 4-76 Zetans.

The 4-76 Zetans are your typical Little Green Men-types with sharp teeth and three digits on each hand, 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, going about the Galaxy abducting beings and performing experiments and interviews on their abductees.