The Lost Brother Quest/Spoiler

Method
Go and find Tarun in the Tiquanda jungle. He is located near the Khazeel Pass, here. Ask him about his brother and tell Tarun you will help find him. Then, walk north to reach the Asura Palace and enter it. Be careful, though, as many Dawnfire Asuri, Midnight Asura, and Hellspawns reside here.

It's unknown how to progress the quest from here. On the very top floor, there is a Sealed Door leading to the room of The Flaming Orchid, but it cannot be opened at this point. Above her, there is a small room with a Sarcophagus containing 3 Small Rubies and to the left and up there is a small room with a chest containing 3 Small Sapphires. You can go down in this second room by stepping on Some Cracks in front of the chest, which leads to a room filled with 4 Nightfiends. There is also a strange Blackboard in this room, which says You read: A golden goblet filled with fresh and innocent blood. A silver chalice filled with snake and scorpion poison. An ivory vessel filled with a wailing lover's tears.

These are the paraphernalia to perform the ritual of youth and beauty.