Umbrage for Umbriss is a Cataclysm heroic dungeon achievement needed for the [Glory of the Cataclysm Hero] achievement, rewarding the [Reins of the Volcanic Stone Drake].
The boss gains this buff when you kill a Malignant Trogg next to him, the buff lasts 20 seconds so you have to time it correctly. While affected, the boss deals 50% increased damage.
[Glory of the Cataclysm Hero]
Patches and hotfixes