Go back to Chelsith and search for 5 clickable tablets. You may need to wait 30-60 minutes for a respawn on the tablets as there are only 4 known locations (If you find #5, please let us know!):
Near the entrance ( 15, 4, 390 )
In a pool ( 162, 1, 250 )
At the Shrine of the Deep ( 434, 44, 130 )
On the ramp near the Shrine of the Deep ( 346, 16, 148 )
Kill 75 Reet slaves in Sebilis - either near sporconids on lower level or near labs on upper level (look for orange dots on your map when you get close).
The zone in to the Instance where the final mob (82^^) is found is in front of where the Avatar of Hate( -1307, 48, -1509 ) spawns. There is an anvil on the ground near that location, click it to zone into instance. (Only Inquisitors on the same step may enter the instance.)