Dauthi

Dauthi is a black creature type used for cards that depict an insane Horror-like race of beings trapped in the Shadows of Rath. All have the keyword ability Shadow. The cards as they appeared in the Tempest block didn't have the subtype Dauthi. It was later realised that a non-human race should have its own subtype, which resulted in Dauthi Slayer in its Time Spiral/Timeshifted form. The other cards were updated in the Grand Creature Type Update.

Storyline
The Dauthi originally lived on Dominaria, maybe with another outward appearance. During the time of their planeshift, the Dauthi were at war with the Soltari. The Thalakos were entrapped in the conflict, despite their neutrality. All three races were caught in the maelstrom of energy that surrounded Rath, and trapped within the "Shadows," the extraplanar space between Rath and Dominaria. They were left in an incorporeal state, unable to communicate with people on either plane, yet able to see into both the Dominarian reality and that of Rath. This predicament led the Dauthi to lose their sanity; it's possible that the Dauthi were already a race close to madness, and their condition provided the last push.

Dauthi aren't content to turn their psychotic nature on each other; some of them are able to seize corporeal beings and drag them to the shadow side of reality where their compatriots are ready to tear them apart.

Shadow Rider
The Shadow Rider of Weatherlight has been mentioned as an original Dauthi from Dominaria. However, in the Grand Creature Type Update it was changed to a zombie. This was partially rectified in the Oath of the Gatewatch update, when it returned to just being a Knight.