A Fused Colony (融合群体, Yuugou Guntai) is a titanic amalgamation of Kabane, animated or otherwise, that form an animated, humanoid shape. Easily able to tower even the grandest of buildings, a colony can be as large as the number of bodies it has accumulated, and a single fallen station seems more than capable of producing enough bodies for one's creation. The Kabane incorporated into the colony seem to be consciously gripping on, or otherwise fused, to each other to form the shape.
The colony has a heart as its weakpoint like any other Kabane, the difference being the sheer size of it - a colony's heart is a Kabane itself, surrounded by a multitude of other Kabane to form the body. The core Kabane seems to be partially fused or encased in a bright blue substance of unknown characteristics, though the rest of the body will do whatever it can to actively protect it, going as far as to "re-knit" the body around the exposed core with more Kabane. As stated by Mumei, the fused colony is "very greedy", taking in humans and Kabane to grow in size, dead or alive.
One such specimen was defeated by Mumei and Takumi in Yashiro station, in which the inhabitants of the former were caught so blindsided they described the incident as being engulfed in "black smoke" (黒けぶり, Kuro Keburi, lit. Black Smoke), having unofficially christened the creature without knowing what it truly was. By Mumei's reaction towards it, it can be assumed that more can and do exist, though seem to be rare as it was her first time witnessing one herself and the rest of the crew seemed entirely ignorant of anything remotely akin to it. It was later reviled to be a man-made Fused Colony that Mumei's brother created. It can only be used by females using black blood. The process can also be reversed if white blood is injected.