There is no special interaction with any bosses in order to get the quest done. The boss kills are simple kill tasks that are completed on the boss's death in World of Warcraft.

Jaina or Sylvanas are located inside the instance.The instances are located at Icecrown Citadel in, well, Icecrown. You fly in through one of the side entrances. The Forge of Souls will be on your right facing the three portals. There is a meeting stone there too. You have to be level 80 in order to do the quests.

The Forge of Souls is the first instance in the group of three that make up the Frozen Halls in Icecrown Citadel.Jaina or Sylvanas will be sitting at the entrance and will give you a quest to kill Bronjahm and the Devourer of Souls. This quest is straightforward.

We don't talk about the trash much because it's all the same stuff, different place.To kill Bronjahm you'll want to DPS him down. He'll cast a spell to separate someone's soul from their body which will create a soul shard. This shard will heal him if he's nearby. You can kite him away and kill the shard, kill the shard with him nearby, or ignore it if you have enough DPS and feel especially lazy. At 30% he'll cast a soulstorm spell. Step into it and you'll take massive damage. He'll fear you into it too.

The Devourer of Souls is rather easy as well, but can end up with your DPS dead if they're not careful. He'll put up a Well of Souls on the ground that does intense damage. He also will cast Mirror Soul which mirrors a percentage of your damage back at you. STOP DPS during that unless you have a super healer. He'll do an "Unleashed Souls"attack that spawns tormented souls that do joke DPS but can get pretty tough if too many stack on you.

Wailing Souls is an attack that will either attack clockwise or counterclockwise in about a 90 degree arc. You can try to avoid it or just take the 5k damage and laugh it off.