From WoWWiki
Following the Warsong clan's initiation of their logging operations in southern Ashenvale, the Night Elf Sentinels launched a massive counterattack to drive out the Orcs. The Warsong clan had even attracted the attention of the ancient, reclusive demigod, Cenarius, who personally took command of the Night Elf forces moving against them. After barely managing to repel several savage attacks from the sentinels, defeat for the Orcs seemed imminent. The Shamans and Witch Doctors under Hellscream's command then sensed a powerful energy emanating from the woods, which turned out to be a well fouled with the Blood of Mannoroth. After defeating the satyrs guarding the befouled well, the Warsong Clan drank the blood and became Fel Orcs imbued with a bloodlust and demonic powers. With these new powers, the Orcs easily overcame the Sentinels and slew Cenarius, forcing the Night Elves to retreat back into the depths of the forests.
