He was a gnoll seer in the western mountain part of the Tirisfal Glades and led a smaller tribe of gnolls to the west from Deathknell, in the other side of the mountains, safely isolated from Lordaeron's humans. He led his kin with pride and peace, they were rarely participated in battle, instead they were hunting in the mountain forests and rivers for beast and fish. He was a wise and very intelligent leader, and he always took care of the tribesman. He was interested in knowledge at all times, so he even learned the language of the humans. In order to protect the tribe, he began to study the astral planes, and the usage of elemental energies, what was different of the gnoll's originally shamanistic culture. He wanted power to protect those who was kind to him, and to discourage others from attacking. As he got older, weeks of practice have become years, so he learned to use ice magic with deadly efficiency, and he gained respect in other's eyes.
But then the Scourge invasion came. Though he felt some disturbance before, he couldn't understand what it was... until the woods around them became loud from the march of countless Scourge soldiers, not only dead humans and elves, but Rothide Gnolls, remnants of other gnoll tribes of Lordaeron, he once knew.
His worst fears came alive... for the first time, he couldn't shelter his tribe from danger. As the undead hordes ravaged the village, and spread the Plague, none of them remained alive. Yet he was so efficient, that no undead was able to touch him.
After the battle, he was so exhausted, he barely dragged himself to a nearby valley, where he began to feel the first symptoms of the Plague. Afraid of becoming a Rothide, he used up all the mana remained in him to encase himself in a tomb of ice, hibernating himself, thus he escaped from the Lich King's tyranny.
After four years, his tomb ran out of power and began to melt. He regained consciousness, and was utterly amazed, that he was practically 'alive', but his heart wasn't beating at all. Then his tribe came into his mind, and ran back to the place, where his home stood once. He found nothing else than the remains of the wooden cottages, and crude bones of the fallen gnolls. He collapsed in the middle of the ruins, and released a great howl of hatred and sorrow.
The howl hit the ears of Sylvanas Windrunner, leader of the Forsaken, who felt his fury, so she spoke to him through the winds. She explained all the situations to Chil'thaw and convinced him to join the Forsaken. In several days of time, he arrived to the doors of the Undercity. After the regular embalming process in the Apothecarium, even the masters of the Mage Quarter was impressed, after he demonstrated his power, that was fueled by his rage and wish for revenge. For this power, Sylvanas recruited him to the Fearsome Five with promises, that he will be able to draw blood for his beloved.