Erg Krow was a Jedi Master during the era marked by the Old Sith Wars. When the Great Sith War erupted between the Galactic Republic and the Sith Empire, Krow was stationed at the Order's enclave on the lush planet Mustafar.
Krow was present when the Sith attacked the world. The Jedi used a crystal to enhance their powers and give them an advantage in the battle. Somehow, the crystal self-destructed, having drastic consequences for the world. The crystal's explosion caused Mustafar to go off its orbit and caused the planet to turn from luscious green, to hot, molten lava. The only survivor of the cataclysm was Erg Krow, who survived by shielding himself from the blast with the Force. Even though he was able to save his own life, he was left in terrible pain. He dragged what was left of the crystal to a cave and used his powers to make a shield around it, making sure that no one would claim the crystal ever again. After ensuring that the crystal would not be misused again, Krow succumbed to his wounds and died within the cave. His shield remained in place for many centuries after his death but eventually it faded as well and the crystal was left unguarded.
During the reign of the Galactic Empire nearly four thousand years after Krow's death, Jedi Master Obi-Wan Kenobi and a spacer he was traveling with discovered the cave and attempted to destroy the crystal, which had become active again. In the cave, the pair encountered the Dark Jedi Vartonis who entered into a vicious lightsaber duel in an attempt to lay claim to the crystal. Whent he spacer overpowered Vartonis with the aid of Kenobi, the pair quickly destroyed the crystal.