Anomen's Companion Quest - Baldur's Gate 2
Anomen's Companion Quest begins after Anomen has been in your party for 5 days and you're in an outside area. You'll be approached by a messenger who tells you that Anomen's sister has been murdered; Anomen will ask to return to his house in the Government District of Athkatla. If you take too long to visit Anomen's house (5 days) after getting this message he'll leave your party so don't delay too long.
The building you're looking for the in the Government District is marked on your map, Delryn Estate. Inside you'll find Anomen's father who asks Anomen to take revenge on his sister's killer who goes by the name of Saerk Farrahd. At this point in time the quest will split with 2 different outcomes as you're allowed to encourage Anoment to seek revenge or justice.
Encouraging Anomen to uphold the law and seek justice will earn you the best reward for this quest. Not just the most EXP overall but Anomen will also earn +4 Wisdom for following the "good" path. Below I will give you information about each path.
Get Revenge: Visit the Estate of Saerk Farrahd in the Bridge District and eliminate everyone inside of the building. There will be a scene inside where Anomen kills Saerk's daughter in front of him for which your entire party will get -2 Reputation. Anomen's father will be pleased if he goes this route but Anomen will fail his knight test.
Get Justice: Speak with Bylanna in the Council of the Six building which is found in the northeastern portion of the Government District. Bylanna will tell you that no evidence has been found to indict Saerk and you'll be given one last chance to let Anomen claim revenge. Convine Anomen that's a bad idea and you'll earn some EXP.
As previously stated if you decide to go down the path of revenge you'll have to visit the Estate of Saerk Farrahd which is in the central portion of the Bridge District. The building is marked on your map and pretty easy to find but if you need help check my screenshot above.
Regardless of the approach you take to this quest after you decide on a path you'll have to wait some time until Anomen reaches Level 12 and/or until 10 days pass. After enough time passes you will be approached in Athkatla and invited to speak with Ryan Trawl in the Radiant Heart building in the Government District.
This is essentially a ceremony that will either admit Anomen into the order or fail him. If you chose the path of revenge then Anomen will fail his knight test and he'll be removed from the order. Anomen will also switch in alignment from Lawful Neutral to Chaotic Neutral.
If you chose the path of justice then Anomen will pass his knight test and he'll be approved to join the order. Anomen will switch in alignment from Lawful Neutral to Lawful Good and he'll also get a permanent bonus of +4 Wisdom. I've broken down both sets of rewards below in an easier to read format for those interested.
Pass Knight Test Rewards: +4 Wisdom; 10k EXP for party and 50k EXP for Anomen. Alignment Change from Lawful Neutral to Lawful Good.
Fail Knight Test Rewards: 5k EXP and Anomen's alignment changes from Lawful Neutral to Chaotic Neutral
Once the ceremony is over this quest will be completed and Anomen's personality will change. Depending on what route you took he will get different dialogue options and will behave differently.