Chaos Well from Warcraft III.
The Blood of Mannoroth, the vile fluid that ran through the veins of the Destructor, was used to corrupt the orcish race and bind them to the will of Kil'jaeden. Prior to the opening of the Dark Portal, Mannoroth was summoned to Draenor by Kil'jaeden, who instructed the orc warlock Gul'dan to spill the Destructor's blood into the empty meditation pool of the Temple of Karabor. Sometime later, assembled at the Throne of Kil'jaeden, the vast majority of the orcish race — the first being Grom Hellscream and his Warsong clan — drank the burning blood, and became minions of the Burning Legion. Only a select few, most notably Orgrim Doomhammer and Durotan's Frostwolf clan, refused to drink. After the Horde was defeated and rounded up into internment camps, the orcs began to suffer serious withdrawals and sink into lethargy, or succumb to demon-crazed madness. Hellscream resisted the maddening bloodlust and paralyzing lethargy that was consuming his race for many years...until the Destructor's blood flowed again.
Mannoroth — at the advice of the Dreadlord master of the Scourge, Tichondrius — spilled his blood into a fountain of life, knowing that the orcs would eventually find it. This would have the effect of not only returning the orcs to their blood-crazed past, but also dealing with an old foe: Cenarius himself. Hellscream and his Warsong clan were hunted by the forest demigod Cenarius and the night elves due to their lumber operations in Ashenvale. The Warsong clan were in a loosing battle but a Darkspear witch doctor sensed a power nerby. Hellscream and his Warsongs went to the source of power that resulted to be the now-corrupted fountain of life, the Chaos Well. Hellscream's witch doctors, who had sensed the power of the fountain, now warned him that the fountain was cursed, but the Warsong chieftain and his forces drank from the corrupted fountain anyway. Later, Cenarius was slain by the newly empowered Warsong orcs but moments after their victory Mannoroth appeared before them and slaved them once more. However, with the help of Thrall, Hellscream managed to break himself free from this second blood pact and faced Mannoroth in a canyon. Using all the strength he had left, Hellscream made a devastating blow against the pit lord, shattering his plate and spear by driving his axe deep into the demons body. In an explosion of demonic energy Mannoroth the Destructor was no more, but the effects of this left Hellscream mortally wounded. As he lay on the ground, the crimson haze lifted from the eyes of Grommash Hellscream and his clan mates; the blood curse which had damned his race for generations was finally over and thus the orcs were free from their enslavement by the Legion forever.