This quest is activated only if you saved Delorus in Fort Joy.
1. Temple Of Rhalic - Delorus
2. The Nameless Isle - Temple Of Tir-Cendelius
Somewhere near Temple Of Rhalic you will find the bodies of the Magisters. Delorus will be standing next to them . He will recognize you and ask for your assistance in finding Alexander. You'll have to escort him to Temple Of Tir-Cendelius .
Until you reach the destination he will sort of become part of the team, participating in any combat situation. You can control him as well. Unfortunately, Delorus isn't the most resilient character, so you have to watch him.
The entrance to the Temple Of Tir-Cendelius is guarded by the Shriekers.
You can get rid of them using the Source Vampirism or the Purging Wand. This weapon is easily obtainable, since the mages of the Black Ring use it. Right at the entrance, you will be halted by a guard, whom you should ask about the whereabouts of Alexander, in order to finish the quest.
Reward: 50150 experience points+ Delorus' Bow