Grim Batol, once one of the greatest dwarven fortresses, is now home of the Dark Iron clan and the Twilight Hammer. It features a 5-man dungeon, as well as a raid (Bastion of Twilight). As announced on BlizzCon ’09, a new raid will be added to Grim Batol in the last progression patch of the Cataclysm expansion, and its final boss will be none other, but Deathwing himself.

Bosses in the 5-man consists of:
General Umbriss
Forgemaster Throngus
Drahga Shodowburner
Erudax

TotalBiscuit posted a video of the new 5-man Cataclysm instance Grim Batol