In the sidequest "Thanator tooth" you bring a Thanator tooth to Morgan and Clax.

When you first talk to them they ask if you can handle yourself and dare you to bring the tooth of a Thanator, thinking it's an impossible feat.

The only place where you can find a Thanator is in Blackwhisper Cave. Go there, kill a Thanator and you automatically carry the tooth after the battle.

Talk to Morgan again and he will give you a reward of 25 Pix.