The Bullsquid is a bipedal, highly aggressive creature that appears throughout the Black Mesa Research Facility due to the dimensional rift. Bullsquid are able to survive, if not thrive, in environments that are unfriendly or even toxic to humans, including sewers and pools of radioactive, chemical, or biological waste. On Xen, Bullsquids are found drinking from pools of an unknown liquid that has healing properties for humans and Vortigaunts.