Tetrarch Talloth:
Tsk tsk. I will tell you one more time. I need the omen beast's eye, Taint Stone and succubus' blood. You can obtain the first component by killing the omen beast and taking the jewel that is embedded in its eye. The second material can be gathered by hunting stink zombies or tainted zombies, the undead that wander the School of Dark Arts. The final material can be obtained only by killing the succubus, who resides in the deepest lairs of the School of Dark Arts.
When you have gathered all three materials, bring them to me.