X-Com Enemies - Ethereal

The Ethereals, they quickly show you why they are on top of the alien hierarchy when they demonstrate their mastery of psionics. Once you see one of these guys, it is highly recommended you focus all the fire on them you can to bring them down quickly. Otherwise, they will start mind-controlling your troops or unleashing psionic rifts that devastate an area. One upside since Enemy Within was released, they now can no longer reflect your attacks or at least it's chances of happening have been drastically reduced. Regardless, they are capable of causing serious havoc if left standing for too long.