Normally, a knife that mounts on your rifle its called a bayonet, unless it’s the Wolfhawk. A joint venture between Battle Blades and TOPS Knives, the Wolfhawk series utilizes a sheath that incorporates a Mil Std 1913 rail compatible mount.
Offered in two blade (Hunter and Tanto) and two handle (micarta and paracord) versions, it features a 3-1/4″ blade made from 1095 High Carbon steel (RC 56-58).
When I see things like this that are done simply because they can be, I fear we have invented everything.