Devilsaur Tooth

Devilsaur Tooth is a trinket exclusively for hunters that grants your pet increased critical strike rating until the next time it gets a critical strike.

Source
Devilsaur Tooth is a quest reward from the quest The Green Drake which starts with Ogtinc in Azshara. To complete the quest, you must turn the following item to Ogtinc:
 * 1 Tooth of Morphaz