Demonseed (実験用生体培養卵 デモンシード Jikken-yō Seitai Baiyō Tamago Demonshīdo?, lit. "Cultivated Egg of an Experimental Organism Demonseed") is an enemy from Operation C.
It is a large, stationary, pod-like alien egg that bursts open and releases three infant aliens either when shot or approached. Some can be found still at an underdeveloped state and thus are harmless; others are static and also cannot attack nor be destroyed; only pulsating ones have the ability to release enemies. They have no other means of attack and will die after giving birth.