Long Way Home

You'll most likely want to form up a solid party of one tank, one healer and two damage dealers before journeying out of Kirkwall. On the way to this mission you may come across the start of Blackpowder Promise, but it is a completely unrelated task. Once at Sundermount talk to the two Dalish guards and enter the encampment.

After talking to Keeper Marethari you'll be introduced to Merrill and be sent into one of the mountain's caves. You'll be in for some beefy fights so be sure to stock up on potions from the Dalish store before heading in further. You'll be fighting a large gang of Giant Spiders as you make your way through the cave. Take out the weaker enemies before smashing down the stronger spider leaders. Afterwards you'll reach the exit to the mountain's ridge.

There will be a barrier to the ritual site, however Merrill will lower it by using blood magic. You can gain some Friendship by condoning her actions, though use of blood magic can hurt your Friendships with Anders and Fenris. Make sure to cross the barrier, as the rest of the mountain is crawling with tough groups of enemies that may be too much to deal with right now.

You'll face off against an Arcane Horror, Shadow Warrior and a huge amount of Skeletons. You'll want you tank on the Horror while the rest of the party clears out the lower end Skeleton Archers. After the Horror is dead the main focus should turn to the Shadow Warrior. As with most fights be sure to inflict status debuffs, mainly ones that boost damage such as Stagger, Brittle, and Disorientate.

After the fight, talk to Flemeth and return back to the Dalish. You'll be taken back to the Kirkwall Alienage where Merrill will now reside. Visit her home to start up a Friendship or learn more about her.