Terrafusers are created by Fuse to create Fusion life and cause the infection of Fusion Matter to grow worse. Terrafusers cannot be destroyed or moved.
One or two Terrafusers will be in each zone and are always placed away from NPCs. Around Terrafusers are always Boss-type monsters. Many missions involve the player going to a Terrafuser-spawn spot, where monsters are spawned rather more than in other places where Terrafusers are not found. Terrafusers are found in two sizes; the small ones spawn monsters, the big ones create infected ground (and water sometimes) and grow the infection.