For the Grathalax, the Extractor
quest, there are 2 objectives. The 1,000 Eye of the Jailer will be split among the 2 objectives and you will get 500 Eye of the Jailer when you kill Grathalax
as that completes one objective, and 500 Eye of the Jailer when the 3rd Pain Conduit is clicked. You can safely click 2 Pain Conduits without any penalty.