Fratriphage

"Cry not for the fratiphage's lost wings, for their absence is key to our survival."
Shadow spirits which consume haunts and other spirits. Bull ant-like jaws and mantis-like claws are common features. Tend towards hard shells and bulky armor- as hauntlike beings, their greatest weakness tends to be dismemberment.
Fratriphages, like haunts, have bodies of half-forgotten shadow of existence: 'hard-light' so weak that it ceases to be immutable, cast by a soul so faded as to be unrecognizable. This is known as in certain circles as Desperation.

What defines a fratriphage?

Put simply, a fratriphage gives up on flesh. While one can create exoskeletal growths of bone, the rest of it is forever destined to be that . In doing so, it can never gain a first-order soul.
Consumption of Desperation is analogous to living on candy: tastes good short term, but rots your teeth. To become a fratriphage is to have your teeth so rotted that you can consume nothing but Desperation, lest you choke on food you cannot chew. This doesn't stop fratriphages from trying, though: one of the ways that they tend to die is attempting to consume a human after having already passed the threshold.
Consumption of second-order souls is how they create their armored plates and blades of bone: these are actually more or less the fratriphage trying to make something of the material that is being rejected from their cores. Haunts can incorporate it fully to turn into nightmarish crawlers .
Fratriphages can gain sustenance from spindles, actually: because spindles are half-echo, their souls are so diluted with Desperation that the fratriphage can actually stomach it. Normal haunts treat spindles like any other shadow entity: they ignore them. Fratriphages, of course, are happy to turn on their fellow Darkness spirits.

Serpentine Fratriphages

Fratriphage forms are largely influenced by their environments. In the mundane plane, they're almost exclusively bulky, quadrupedal creatures (sometimes bipedal, and rarely hexapedel). However, those that wander Darkness tend towards more serpentine shapes, and are capable of 'flight' by manipulating ambient darklight. If brought to the mundane world, they are still capable of such flight, though in short bursts rather than as a constant state of existence. Interestingly, these creatures have a tendency to be unaggressive towards humans. This may be a result of their home environments lacking humans entirely. Some argue it may be a result of increased intelligence, allowing them to recognize that consuming a human will kill them; whether this intelligence is gained simply through age or as another consequence of their home environment is even more unclear. (note that in Darkness, haunts kinda just pop up and linger for a while most of the time, since there's no light to kill them, and not much to feed on other than ambient darklight unless they start eating each other)

Binding & Taming

While relatively simple to tame (and even simpler to bind, especially with sorcery), they're quite weak for their relative bulk (after all, despite being so large, most of their bodies weigh very little).