Zeth EditNot much is known about the enigmatic Zeth. They have long, bony bodies and an insectoid appearance. Their mouths look as if they're grinning even when closed and they can have horn-like projections on their heads. As Nevalis says the Zeth they're tracking has come from the northern regions - namely the country of Ysrid, it is possible some or all of them reside there.
While originally thought to be a type of Spiritfolk, Xin revealed that the Zeth as the Spirtfolk's natural predator.
Firi also mentioned she was sent by Zeth to "draw the world."
Zeth are able to break down and mimic most humans with just one glance. As the spiritfolk's predator the Zeth are able to absorb a spiritfolk's wisp, adding them to their own consciousness and gaining access to their abilities. It is unknown if the absorbed spiritfolk cease to exist or continue existing trapped as part of Zeth, though Narn referring to themself as "legion" may indicate that the spiritfolk absorbed are still conscious to some degree.
In the end-of-episode message in episode 108, Jay writes: "Silly Xin, the Zeth are far, far more dangerous than that."