Rasaad's Companion Quest - Baldur's Gate 2
In Baldur's Gate 2 you'll meet Rasaad in the city of Trademeet which can be added to your World Map by speaking with Flydian in the City Gates portion of Athkatla. Flydian will begin the Animal Trouble in Trademeet quest which adds this town to your World Map. In Trademeet you'll have a short scene involving some Monks near the fountain in the middle of the zone; after witnessing this scene you'll be approached by Rasaad.
Recruit Rasaad into your party and then visit the City Gates portion of Athkatla again, this time with Rasaad. You will be approached by a Cloaked Figure who will ask for Rasaad (pictured above). Go through the dialogue with this person and it will begin the quest Rasaad's Journey which is his Companion Quest.
Once you accept this quest you'll get a new location added to your World Map, Abandoned Amphitheater. This is our next destination for continuing Rasaad's quest. For a detailed overview of the Abandoned Amphitheater map and all of the side activities here follow the link provided - this page covers solely Rasaad's quest.
All we need to do on the Abandoned Amphitheater map is visit the Amphitheater in the northeastern portion of the area. When you approach this area you will be stopped by a guard (pictured above) who will ask you what your purpose here is. You basically have 2 approaches you can take to this area - you can go in guns blazing and eliminate everyone or you can take a stealthy approach and sit through the cult meeting.
The stealthy approach will involve you talking to Hammerhelm (the leader of this meeting) and he'll add Heretic Temple to your World Map before leaving. As for the guns blazing approach, this will involve taking Hammerhelm out and picking up the Note he drops which will add Heretic Temple to your World Map.
I strongly recommend the guns blazing approach as you'll earn significantly more EXP from doing it this way. Before leaving this map I also recommend you visit the Vagrant Blades camp to the southeast of the Amphitheater. Here you'll find a group of adventurers arguing over a belt; much like with the Amphitheater I recommend you kill all of them since they all drop at least 2 magical items (and the magical items are actually really good).
After you complete the Amphitheater event and unlock Heretic Temple on your World Map - the next time you travel from one area to another you'll get waylaid by a group of Sun Soul Monks known as the Tears of Selûne (pictured above). Depending on your choices during the dialogue it's possible to convince all of the monks to leave peacefully or to provoke a fight.
You can fight all of them or just a few of them depending on your choices. I would actually recommend fighting all of them that way you can maximize how much EXP and loot you get from this ambush. They drop a few unique magical items that you can't get anywhere else in the game. All of the magical items they drop are listed below.
When you arrive at Heretic Temple you'll have 2 interactions before you arrive at the actual temple. Someone named Herath will approach you and you'll be able to give her guidance (if Rasaad is with you) and you will also be stopped at the bridge leading to the temple. There are numerous different options for each of these interactions, what you choose for either doesn't matter.
There are a few things you can do outside of the Heretic Temple before entering; for more information about this zone as a whole follow the link I provided. It'll take you to my overview guide for this zone which gives you a Bird's Eye view of everything to find. The most important thing outside of the Heretic Temple that you should do immediately is recruiting Wilson to your party and finishing the Where's Wilson? side quest.
If you don't want to drop everything you are doing right now to go out of your way and complete this quest then you can use a Console Command later on to spawn Wilson when you're done here. The alternative is you just don't complete the Where's Wilson quest. For more information about the Console Command head over to the quest page I linked.
When you're ready to proceed with this quest head inside of the Heretic Temple. There are a few ways you can do this, you can go through the front door or get Rope from the nearby monks and go through the sky light at the top of the temple and earn 2000 EXP for each party member.
Once you're inside the temple approach the central area for a scene with Collus Darathorn. You'll be given the opportunity to fight him right here and now but I strongly recommend you don't that way you can still complete the second half of this quest. There are numerous "tests" inside of this temple which will offer magical item rewards that you can not get otherwise.
Keep in mind that you should have Rasaad in your party for the duration of this quest. Without Rasaad there will be a lot of EXP and magical items that you will miss out on. How this dungeon works is there are 4 tests that you need to participate in throughout the temple. It doesn't matter what order you do them in so pick whichever you want.
Each time you complete one of these tests you'll be rewarded with 10k EXP and a magical item. Information about each test is found below.
Room of the Bright Moon: 10k EXP and Gauntlets of Aln Zekk is the reward. To properly pass this test you're supposed to follow the path of light until you get to the center of the room. Once you reach the center you'll be asked by "The Truth" to tell him a secret, all of the available options will work just fine. It's worth noting that if you stand in the shadows you'll spawn Shadow enemies that will attack you. You can do this indefinitely farming as much EXP as you want.
Room of Penance: 10k EXP and Cloak of Atonement is the reward. In this room you will be asked to supply information about someone who is disloyal to the cult. You'll have a few different options depending on what scenes you witnessed outside of the temple, any of the available secrets will work.
Room of Pain: 10k EXP and Eyes of the Beholder is the reward. All you need to do for this trial is refuse to submit to the pain and do not provoke the people attacking you. It's impossible to die from the damage that they deal to you.
Room of the Blinding Sun: 10k EXP and Gem of Seeing is the reward. You'll have to fight and defeat 3 Invisible Stalker enemies to pass this test.
Once you've completed all 4 trials the Master of Combat will spawn in the middle of the Heretic Temple. Speak with him to advance the story forward - during your dialogue with him a sentry will enter the room and warn everyone that the temple is currently under attack. It's possible to convince Rasaad to lead the troops during this fight, otherwise the Master of Combat will lead the charge.
Before you exit the temple I strongly recommend you buff up with everything you got and save the game. The fight that is coming up is going to be a difficult one depending on the level of your characters.
You will face about a dozen enemies on the bridge leading into the Heretic Temple. When the battle is over, if the Master of Combat is still alive he'll have some dialogue before heading back inside. You will also have some dialogue with Rasaad when the battle is finished. This dialogue with Rasaad is very important and choosing the wrong dialogue tree kind of "breaks" the quest.
If you want Rasaad to take over the Twofold Temple as its leader you need to choose the 3rd dialogue option, "Calm yourself, Rasaad. This is but a temporary setback." This will open up a whole chain of dialogue which will allow you to encourage Rasaad to lead the temple. If you're successful Rasaad will leave your party (good) and all items on him will be given to other party members. Choosing any other dialogue option will result in Rasaad's Journey disappearing from your Journal and that's it - end of quest.
For those of you who chose dialogue options 1 or 2 instead you can head back inside of the temple and kill the Master of Combat and every Monk inside for their EXP. Aside from that you're done with this zone and with Rasaad's Companion Quest.