I'm not sure about Briskbreeze Tower, but Seravin's Tower is where the Great Troll lies. As soon as you unlock Colossus Blvd, Gloria Krendell (in Olde Town) will give you a new quest. She has you running around killing Dark Fairies, Ghosts, Ghouls, Fire Elves, and more. Then at the very end, you battle the Great Troll in Seravin's Tower and she gives you an entire outfit for your class for level 10. On some of my characters, I wore the outfit until level 20. On others, I discarded all or most of the outfit by level 14.