Act 3 Quest 5: The Blackened Temple - Diablo 2
Quest Location: Travincal
Quest NPC: Deckard Cain
Quest Goal: Defeat the Travincal High Council
Reward: Zealot enemies will now run away from you in Act 3
The Blackened Temple quest begins when you enter Travincal for the first time or by speaking with Ormus after completing Act 3 Quest 4: Lam Esen's Tome. In order to complete this quest what you need to do is defeat the High Council at Travincal and smash the Compelling Orb with Khalim's Will. To reach the Travincal you'll want to head directly north from Upper Kurast to Kurast Causeway; then north one more zone from there.
You'll find the High Council in the north-central portion of Travincal with the Waypoint in this zone always being west of their location. There will always be 3 Super Unique enemies that make up the High Council and they'll all spawn inside of the same building. It can be tricky fighting them all at once so it's recommended you pull them away and try to break them into either a pair or solo.
Once all three of the High Council are dead all that's left to complete this quest and gain access to the Durance of Hate is to smash the Compelling Orb. To do this you'll need to complete Act 3 Quest 3: Khalim's Will. The final part of this quest has you combine all of Khalim's.... parts with his Flail which will make Khalim's Will. Use this to smash the orb and complete both of these quests.