hound of tindalos

The titular race of monsters from Frank Belknap Long's short story Hounds of Tindalos, which was later incorporated into the Cthulhu Mythos when it was codified by August Derleth.
While sometimes pictured as canines, their appearance is "too foul to be described". They are said to inhabit the angles of time, while other beings (such as humankind and all common life) descend from curves. As such, they can materialize through any corner if it is fairly sharp (120° or less). A person risks attracting their attention by traveling through time.

They also made an appearance in Dark Souls III as Sulyvahn's Beast, which hunt down the player who time traveled into the future.