Zul’jin is the last boss of Zul’aman Instance. He drops 133 & 138 level items. Zul’jin will be able to draw upon the ghostly spirits of each of the four liberated animal gods from the instance and change his own shape to assume their powers. Every 20% of his health, he switches form.

Strategy for all 5 phases you'll find here:
How To: Zul'jin