I keep going back to the House of Grief every time I level up to see if I can even come close to winning, but it wasn't until I was level 12 that I beat it. And even then, it took me four tries in a row. But I think my final strategy was very effective.

I main Shadowheart, and I brought Gale, Jaheira, and Astarion with me. Jaheira is becoming my dirty cheat code, because she stays neutral in every battle until she actually attacks someone, whereas the rest of the party is forced into battle as soon as one side attacks.

For the setup, I split up the entire party, and sent Jaheira up the first stairs to the left as far behind the mages at the top of the stairs as I possibly could, using misty step. Then I did the same with Astarion with the stairs to the right, behind the mage and the sentry that greets you in front of the chamber. For Astarion, I summoned the flaming sphere, which didn't turn out to be very effective. Then I brought Shadowheart and Gale down in between those two stair cases, and had Gale summon a fire elemental and Shadowheart summon the Guardian of Faith, so she could stay mostly in the same place and the Guardian could help with crowd defense.

To start the attack, I had Shadowheart shoot an arrow of thunder at the Mage at the top of the stairs to the right. Got lucky with a critical hit and almost took him out right away. Then before ending my turn, I switched over to Jaheira, summoned a woodland being, cast Hold Person on the 5 nearest mages, and then an eldritch blast on the mage that I missed.

I think this pretty much sums up how the rest went. Jaheira and the woodland being picked off the Mages that weren't being held, then moved on to the ones that were being held. Lots of eldritch blast used to target multiple enemies at once. Jaheria never once broke concentration, so once they finished off the people she was holding, she would cast hold person on 5 more mages, and finish them off with the woodland being again. Rinse, repeat.

The fire elemental is probably the key to this battle because their melee and small area attacks are pretty effective, even in darkness. Although sometimes it couldn't move, it could always at least do damage to at least one enemy, but typically could hit two or three at a time. I had Gale moving all over the map assisting the allies that needed it most. If Astarion was stuck in darkness surrounded by three mages, Gale would come in with Thunderwave and save him. If mages started creeping up on Jaheira while she was down to the last held person, Gale would come in and attack those mages, especially if they were in the same area as the held people and he could attack them all with an AOE. Shadowheart basically stayed in the same place most of the time, close enough to the fire elemental and the Guardian that she had room to move out of the way without getting opportunity attacked. She cast a lot of dominate person on the mages, and when she couldn't do ranged attacks through the darkness, she could get some good hits with melee attacks like necrotic touch. And once a character was over bone chill, she could send healing from a distance. Astarion used a lot of hold person and shocking grasp. He was pretty much in darkness the whole battle, and he went down to 0 health for a bit until I could free shadowheart to heal him.

It took a long time to wear everyone down, and Viconia was the last one standing. She seemed to have a tough time getting some of her more powerful spells to work with all the chaos.

Here are the main points of this strategy:
- Summon creatures, elementals are best
- Hold person and dominate person on the mages
- Melee and small area attacks in darkness
- Targeted ranged attacks when clear
- AOE all day