Spawns after killing several Bristlecone Terrors (which can be attacked after killing the Deranged Guardians). Randomly, one of them will call out for Gormtamer Tizo to save them, which will spawn Chompy (with Tizo on its back). Taming or killing Chompy will spawn Tizo.
Spawns when you get near the Decayed Husk treasure.
*Level scaling: In Shadowlands most NPCs will scale with the Hunter's level, within the constraints of their level range. Hunters can tame regular NPCs up to 2 levels higher than them, but can only tame elite NPCs of the hunter's level or below.