The CK-8 is a quadruped tracking platform that shouldn't exist according to Arcturus's official product catalog. It resembles a CK-5 Bloodhound in basic chassis design but with significant modifications: the skull housing is elongated and contains sensor equipment that doesn't correspond to any known detection technology, the joint articulation allows the legs to bend in directions that standard mechanical engineering shouldn't permit, and the unit has been documented appearing in locations it couldn't have reached through any conventional path.

Arcturus's paratechnological division — which Arcturus denies having — developed the CK-8 to track targets through what internal documents refer to as 'angular space.' The unit doesn't follow physical paths. It navigates through geometric relationships between hard angles — corners, edges, intersections of flat surfaces — appearing to phase through walls at points where two or more right angles meet. Field observations describe the unit as visible only at corners, as if it exists in the spaces where straight lines intersect and is invisible everywhere else.

The CK-8 has been deployed exactly seven times. In all seven cases, the target was found. In three cases, the target was found in locations they hadn't told anyone about. In one case, the target was found inside a sealed room with no windows or doors. The CK-8 cannot be outrun because it doesn't use the same space you do. It cannot be evaded because it tracks through geometry, not chemistry or heat or sound. It finds you because you exist in a space that has corners.