NoSt109,525 Locked 03 Dec 2020 03 Dec 2020
*** Spoiler - click to reveal ***In the beginning of the Throne of Bhaal campaign you will get teleported to the pocket plane and you will meet Sarevok once again. Then he will offer to join your party. Accept and you will get this achievement.
If you don't really want to have him in your party, reject the first time, save the game, talk to him again and accept, then reload.