The Bloodhound (aka Chainsaw) is a new trap added to the game in a recent update. It's modeled after a chainsaw. It functions similarly to the Blade, but with some differences. Unlike Blades, a Bloodhound can't be placed in the air; it can only be placed on a wall, floor, or ceiling. However, the Bloodhound is able to freely move over whatever surface it's been placed on, and if the player touches that surface the Bloodhound will go after the player until they either get away or are killed by it.
There is an exception to this though: when you place the Bloodhound under the surface of a block with the bottom on the edge acts as a blade. You can't see it, but a small rectangle comes out and can kill you if you land there. wherever that may be.