Bonefang is the mount of Amarth and serves as the second boss in The Necrotic Wake. Taming Bonefang will prevent you continuing with the dungeon and it probably shouldn't be tameable at all. Consider taming a Flayedwing Fleshripper instead.
Available after completing the main story. Located at the back of the House of the Chosen.
Level scaling: 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.