Grim Batol, once one of the greatest dwarven fortresses, is now home of the Twilight Hammer and the corrupted Black Dragonflight after the battle between the Wildhammer and the Dark Irons. The 5-man dungeon lies to the west of the Twilight Highlands. Players can enter the dungeon on Normal-mode at level 84, requiring minimum ilvl 305 to queue up. The dungeon is notable for having players ride dragons as vehicles over the extensive trash, bombing them to get them to low HP. With the numerous dragons as trash, it's also an excellent place for skinning.

Players who turn in Vengeance of the Wildhammer with Dwarf Rune Stone will grant the party Vengeance of the Wildhammer: While infused with the rage of the dwarves who lost their home, your critical chance is increased by 5%.

From the Blizzard Community site:
"Don't be fooled by Grim Batol's humble exterior; many of this mountain fortress's desecrated chambers are buried deep in the Twilight Highlands. Once the stronghold of the Wildhammer dwarves, and later seized by orcs as a prison for Alextrasza, the city is now in the clutches of the Twilight's Hammer cult. Heroes brave enough to infiltrate the brooding depths of the stronghold must confront Deathwing's agents to thwart the mysterious evil within.

With the reemergence of Deathwing into the world of Azeroth, the black dragonflight and Twilight's Hammer cult have driven the red dragons away, and converted the dwarven-forged stone halls into a training ground. Grim Batol has once again become a battlefront.

The red dragonflight has begun to assault the gates of Grim Batol from the air, but their assault is jeopardized by the black dragons, who fight back with characteristic intensity and viciousness. If the red flight doesn't receive support soon, the battles raging around Grim Batol will calm at last - and the fortress will rest firmly in the grasp of evil."