The Bosstiaries often have information that the dungeons never really give you; for example, who knew that Auriaya was the Titans' librarian? Nobody, that's who. We just wondered why the heck she was wandering around Ulduar with a bunch of cats and a bad attitude. But now you can go into the Frozen Halls and know exactly who you're fighting and why, replete with marks on the map indicating the position of the bosses and the instance entrance.
The Forge of Souls sees us freeing the souls of innocents from Arthas' Soul Grinder machines, run by Bronjahm, Godfather of Souls. Guarding the machines and preventing souls from escaping is the Devourer of Souls.
The Pit of Saron is Arthas' saronite mining operation; Krick, a leper gnome, oversees the operation from atop his abomination, Ick. Forgemaster Garfrost shapes the saronite into weapons of destruction under Arthas' command, and Scourgelord Tyrannus lords over the pit with his fearsome Scourge powers.
The Halls of Reflection are Arthas' private quarters, guarded by his lieutenants in life, Falric and Marwyn. Inside, Arthas himself keeps Frostmourne locked away from those who would try to use it against him.
Patch 3.3 is the last major patch of Wrath of the Lich King. With the new Icecrown Citadel 5-man dungeons and 10/25-man raid arriving soon, patch 3.3 will deal the final blow to Arthas. WoW.com's Guide to Patch 3.3 will keep you updated with all the latest patch news.