Warhammer 40,000: Mechanicus

Keep doing missions for Captrix (fifth down). This is the mission after defeating Ubjao. Defeat Ekropis, mission will end and cheevo will pop. Ekropis started with 30hp and 5 energy armor. Ekropis will swap places with another creature when you try to damage it. This happened to me maybe five times then it stopped warping around. One it stayed in place then I unloaded my strongest attacks. I defeated several of the additional creatures first while it was swapping around as well.