This last quest of the cursed scroll given by Fabio in Noble District will go all the way to Sanctum of the Burning Souls. You don't however need a group to finish that particular quest, since it finished near the entrance to the dungeon.
First thing is to go see Zelata. She'll tell you to throw some powder on the fire, which you can do. Said fire is behind you, after you go back down the couple wood steps leading to Zelata herself. Once done, go back to Zelata and talk to her again !
Then, go to Sanctum of the Burning Souls. From here, you'll have Guardians of the Scroll popping regularly. They can be bothersome if they pop in the middle of a fight, even though they're only minions. Mages won't care at all about them, since their shield will shield all the damage inflicted. They disappear after a short while, so you don't even have to worry about killing them.
After you finally get to Sanctum, simply enter the dungeon, and activate the white statue near the entrance. The statue will become tainted with black spots, but you're done !