Speak with Hierophant Prime Jarrakas. ( 625, 253, 1337 ) Copy/waypoint 625, 253, 1337 (ensure this step is done and the quest reads 'Ensure Choosooth's mission success' before leaving for Kunzar Jungle)
Complete the instance,then go back and find Chosooth who is in the very back behind last named ( 38, -5, -1215 ) Copy/waypoint 38, -5, -1215.Follow the floating heads and Walk through the illusory wall ( -16, -5, -1130 ) Copy/waypoint -16, -5, -1130, down a hallway all the way to the back. Talk to Chosooth to receive the Vial of Iksar Blood. If you have completed the quest Hold on to the Phylactery you will not have to return to the Hierophant, you will find Chosooth automatically, reveal to him that you have the phylactery and not Venril, and he will give you the Vial of Iksar Blood automatically.
