The master of the Hounds of Tindalos, Mh'ithrha is the mightiest member of that strange species. Although it is invisible, it's physical form resembles a gargantuan wolf, similar to the beast Fenrir from Norse mythology.
Mh'ithrha has been engaged in a war with Yog-Sothoth for all of eternity; stories of this conflict are the stuff of legend in the Cthulhu universe, and the fact that it has not been annihilated by such a being gives a hint to the true extent of Mh'ithrha's power.
- Mh'ithrha made its only appearance in Bruce Ballon's Call of Cthulhu Roleplaying Game splatbook Unseen Masters: Modern Struggles Against Hidden Powers (2001).
- Mh'ithrha was inspired by Fenrir, the great wolf of Norse mythology.