Grom Hellscream was Chieftain of the Warsong clan, a powerful clan. He was the first orc to drink from Mannoroth's blood and thus succumb to the blood curse that would bind the orcs for years to come. When the Orcs had been freed from their bloodlust, after Warcraft 2, Grom met Thrall, and they became friends. But once again he fell to bloodlust when he drank water with demon's blood in it. He killed Cenarius, a demigod. He eventually freed orcs from the bloodlust once and for all by sacrificing himself to slay Mannoroth, thus redeeming himself in Warcraft 3.
His remains are located in Ashenvale where a monument is errected in his honor. The monument reads:
"Here lies Grommash Hellscream, Chieftain of the Warsong Clan.In many ways, the curse of our people began and ended with Grom.His name meant 'giant's heart' in our ancient tongue. He earned that name a hundred-fold as he stood alone before the demon Mannoroth - and won our freedom with his blood.Lok'Tar ogar, big brother. May the Warsong never fade.-Thrall, Warchief of the Horde"
The monument is located at Demon Fall Canyon in Ashenvale, where he fell.
During WoW: The Burning Crusade expansion, his son, Garrosh Hellscream, was located in Garadar in Nagrand, a long quest chain that brings Thrall to Garadar, triggers an event that summons a reenactment of the fight against Mannoroth.
Grom's axe is called Gorehowl and in WoW: Cataclysm, it is now wielded by his son and the current Warchief Garrosh.