As you finish Quest 3: Khalim's Will, don't be hurry. The following tasks need you to collect items so as to compose the powered-up Flail, destroying the Compelling Orb and the tasks are completed. In the process, Quest 4 and Quest 5 can also be completed simultaneously. Let's discuss in detail.
How to find Khalim's Eye?
Find the Spider Cavern in the Spider Forest, not the Arachnid Lair by the waypoint. Into the Spider Cavern, a large mount of Flame Spiders appear. Kill the mini-Boss beside the golden chest and open it to get Khalim's Eye. With numerous items dropping, you can check them by Alt button.
How to find Khalim's Brain?
After you find the Khalim's Eye, go ahead to Flayer Dungeon in Flayer Jungle fromthe Spider Forest which you can find beside Gidbinn in Quest 2. you will finally find the golden chest in the third floor of Flayer Dungeon. Here I suggest walking down the edge of the map in a clockwise direction because I found it on the left of the map. It's easy to kill the mini-boss Shaman to get Khalim's Brain by opening the golden chest.
How to find Khalim's Heart？
Reach Kurast from Flayer Jungle and seek Khalim's Heart in the Sewers city. On thing need to be noticed that you can't open the second floor until you find Sewer tie rod. The second floor is kind of small. Kill the monsters in it and open the golden chest to get Khalim's Heart.
How to find Khalim's Flail and to complete Quest 5: The Blackened Temple？
Search for the waypoint in Travincal so as to ensure enough time back to campsite. This portion is kind of difficult. You need kill all the Council Members and surrounding monsters, so you'd better remain the best state. It's necessary to prepare some resist Diablo 2 Resurrected Items due to the sustained damage of Toorc Icefist and Geleb Flamefinger when they died. Turn them into the powered-up Flail with Horadric Cube, then destroy the Compelling Orb of the Council. The passageway appeared is the place of Quest 6.
How to Quest 4: Lam Esen's Tomb
To complete this task, you need go back to the previous place. Entering Kurast for the first time, talk with Alkor. He will ask you to search Upper Kurast, the Bazaar, and six graves of the Causeway. Fortunately, we only need enter the ruined temple of the Bazaar, where you'll meet Battlemaid Sarina. I advise handling all monsters before meeting her or you'll be at a loss. Picking up the book on pedestal and taking it to Alkor, you'll increase 5 modifier points.