Cerberus: The construct known as "Cerberus" is a force field containing particles of antimatter, which takes the form of a large fog bank. It is sentient, to a degree, and can recognize certain markings or symbols, like a badge. It is immune to almost all known weaponry (the companions destroyed the one guarding Redoubt Bravo by tossing an implosion grenade into it). It attacks by sending forth pseudopods of mist, which wrap around its target and inflict horrific electrical burns. Anyone dragged back into the main body is torn apart within seconds. It doesn't need to eat or sleep, making it a perfect guardian. The Cerberus constructs are extremely rare. One guarded the road to Redoubt Bravo (Pilgrimage to Hell), another appears outside a redoubt called Spearpoint (Encounter), and a third guards a redoubt in the Marshall Islands (Shadow Fortress). It is not known if the construct has an actual name; "Cerberus" is the name given to it by Doc Tanner (Cerberus is the three-headed guardian of the realm of Hades in Greek mythology).