Warcraft Lore 6: Grom Hellscream's Redemption

Grom Hellscream and his clan had rallied with the up-and-coming chieftain Thrall in the battles to free themselves from the humans and in the journey to Kalimdor. Mannoroth, the demon Pit Lord and master of the Fel Orcs, wanted to curse Grom and his clan again with his demon blood to make them Fel Orc savages once more under his command.

However, Thrall was able to get to Grom in time to purge the demon blood once again and to cleanse him, but Mannoroth would not give up his orc servants so easily.

Mannoroth, had started to work his fell magic again on him and his clan. This time, Grom would not fall again under the curse, no matter the cost..