im going to try and compile a list of aliens that we have hints of and comfirmation within the lore and other news.(also ive collected some of this info from recon raider videos go watch them he has some good theories) some theories but if I miss anything (I probably will) plz comment:
crabmen: we’ve seen them from the beginning, apparently the grunts and one of the most common of the alien forces.
mutations that we know so far and have been hinted at:( pincer(melee attack) ,grenade launcher(ranged attack), gun(attack), shield(self caring cover), acid spitter head(attack), harden carapace(armor), spike legges(I think it affects their mobility).
crabqueen: they are still working on the name, and intending to be a boss like creature.
they can spawn larva, and generate mist.
mutations: goo cannon( an attack to trap soldiers.), pincers(attack), heavy armor,(adds armor duh)
larva: very little known about these, theory is if they can infest a soldier and turn them into an enemy or will grow into a enemy after so many turns. they could just be little bugs to annoy your soldiers.
sirens: in the most recent news update we got a picture of these, they have offensive capabilities as well as support abilities: we hear within the lore in briefing 4 about a survivor who joins anu watching a group getting immobilized by a sream I would assume that was a siren.
mutogs: Julian confirmed of a anu unit call a mutog handler who can control alien dogs. don’t know if the mutogs can show up as alien units as well.
hammerhead squid mutation: only showed up as concept art for fig.
medusa: show up in the fig campain with an actually name. could also had been the alien that immobilizes that group within the lore.
mermaid: if this is a mermaid Disney got it wrong big time. another model shown during fig.
alien sniper: no official name with this one but another alien concept art within the fig, said to have advanced perception and night vision, fairly certain that its an alien that will try to snipe soldier as it is refereed to as sniper.
snake/arthropod mutation:yes yes plz I want this, another alien concept art from fig.
alien plants: in several stories such as claimed idol and the danger of knowing I think it referees to these alien vines that grow move. they can become very violent and have dragged humans away, possibly an extension from a larger creature, or an individual plant that has been mutated.
this structure might be the focol point for the alien vines.
behemoths: these are to be gigantic beast that can level a haven or base, supposedly you will need to battle on their back and drill poison pods into them to kill them. only one version of this has been seen.
floating creature: shown as concept art and ingame rendering during a developing update little is known about it.
chiron: an artillery alien, not sure what it will be firing, it looks like eggs, or acid,
juggernaut: probably going to be the heavy hitter of the alien forces, but they did say he would have some interesting abilities.
i learned of two other aliens
hand bomb: assuming to be a tiny suicide bomber that latches on to your soilders. mostly assumptions though
swarm: a swarm of tiny insects were mentioned in an interview with the comment that flam throwers would be more affective against them.
other concept art ive found accosted with phoenix point: