Klixen are an insectoid species resembling crabs or beetles that appear in Mass Effect 2. While they bear a passing resemblance to the Rachni, they are not related and are not even sapient. Having been encountered on worlds with harsh environments such as Tarith and Tuchanka, Klixen have been known to share territory with larger creatures such as Harvesters and even Thresher Maws.
Klixen are covered in chitinous skin that is resistant to heat and difficult to break. Their interior body temperature is extremely high and they are naturally resistant to fire, even capable of expelling searing flames from their maws. Even in death they can be threatening as their bodies will detonate violently when they die.
The predatory Klixen attack in large packs and are utterly relentless, advancing on prey regardless of their numbers or strength. They move slowly, but they do not seem to feel pain and ignore impacts, continuously creeping forward no matter how often they are shot.
Klixen are naturally resistant to heat, but shredding ammo can rip through their carapace very quickly and cryogenic ammo can freeze them in their tracks. Even if they are killed while frozen, they will still explode.