There are a large array of specific extra-terrestrial, extra-planar, or just plain extra-human species that inhabit Variant Earth 13 - or at least some tiny fragment of the earth that they've claimed as their own. These entities possess a variety of different motivations for what they do, but few of such inclinations have the benefit of humanity in mind - usually just the opposite, in fact.
Known alien types include the following:
Atlanteans: these fearsome, transparent phantoms of the sea are utterly against the human development of undersea resources, and whenever such a project gets too far, these folks (invisible in the water, thanks to their transparent nature), usually put it down - and hard. Atlanean encounters are increasing of late, what with rising pollution levels irking their ire.
B'ntri: these alien horrors, the subterranean spawn of a rogue planet adrift for eons in the black void of interstellar space, managed to escape their home world thanks to technology left on its surface by its original sentients. These super-carniverous murder machines are now free to plague known space with their horrific eating habits, and are a threat to everything they encounter.
Dwarves: these stout folk, hailing from the extradimensional realm of Nidavellir, have been slowly making their way to earth over the years, mostly because a) they easily blend in, and b) they seem to enjoy the exploration of it, for some reason. Furthermore, studies indicate that this trend will only increase over time, as the sheer numbers of dwarves on Earth is multiplying rapidly...!
Elves: the by-product of intermingling between fairies and humans (often via their former thralls, the pixies), elves have stablized into a proper species in their own right - save for outliers who betray their faerie origins a bit more than most. Elves tend to stick to their own kind, finding human civilization noxious and faerie civilization (such as it is) abominable.
Mhunghus: whether it be a single Mhungi or several Mhunghus one encounters, one cannot help but be stunned by the amazing intelligence they wield, an intelligence that the Agency believes has been pointed towards the Earth for quite some time; it is believed that these psionic, fungal lifeforms may have evolved on a world near our own.
Pixies: formerly human in both nature and stature, pixies have drifted apart from their taller brethren for reasons that are still debated. Regardless, they have devolved into petty tricksters, and truly delight in wielding their meager skills for naught but their own amusements - and humans are most often the target of their mirth. When they even bother with people at all!
Vampires: though the exact origin and nature of the once-human creatures traditionally known as vampires is unclear, it is definitely a fact that each and every one of these evil, crafty creatures constantly hungers for one thing: blood. Human blood, preferrably. If encountered, these beasts should be destroyed as soon as possible, before they make a lunch of you.
Zombies: a grave menace to humankind, zombies are the reanimated dead. Thirsting for human flesh despite a lack of any biological need, the hunger that drives the undead causes them to perpetually shamble after the living. While some zombies occur naturally, the vast majority of such creatures are manufactured as cheap labor or muscle, only to have them escape into the wild.