Genetically identical to each other, sectoids are physically weak, but possess psionic abilities such as “mind merge”, which one sectoid can use to boost the health and combat power of another.
Although thin men have been genetically modified to look like humans, the resemblance is only skin-deep: they release a cloud of green poison when they are killed.
Part biological, part mechanical, the floaters’ distinguishing feature is a pair of back-mounted jets that allow them to hover above the battlefield.
Chryssalids are fast and deadly arthropods with tough chitin exoskeletons and poisonous claws. Their method of reproduction is terrifying...
Armed with grenades as well as plasma rifles, mutons serve as the aliens’ front-line infantry. They are powerful and aggressive brutes that react unpredictably when wounded.
Found only inside UFOs, the mysterious outsiders materialize out of glowing crystals. Once killed, an outsider will disintegrate completely, leaving no corpse.
Shape-shifting cyberdiscs switch between their flat, saucer-like forms and their spiderish assault forms. It is unknown whether they are robotic constructs or sentient beings.
Larger and even more heavily armored than mutons, berserkers possess a “bull rush” ability that allows them to charge at an enemy, obliterating almost anything in their path.