Warlock was the High Wraith of the wraith lords.
He was originally a Wizard named Edric Blackhawk but during the Neverside Wars, he formed an alliance with the wraith lords and became their leader and could use a wizard's own magic against them. During the last days of the wars, Warlock faced Caractacus Crowe and used his magic against him. But Caractacus's hobgoblin companion Randal Moon was able to stop this by chopping off Warlock's hand (which later became the Key of Bones).
Warlock was defeated but not destroyed and planned to leave the Neverside and unleash chaos in the world. After making a cloned Key of Bones, Lyzera used it to contact Warlock from the Neverside.
Warlock told Lyzera that she could have the Neverside once she let him into the Dayside via The Doorway of Long Shadows. However Lyzera secretly planned that once Warlock came through the doorway, she and the other Nekross who extract his and the other Wraith Lords magic. After arriving at Blackhawk Abbey (where the doorway is) along with her husband Varg, Lyzera frees Warlock and gives him the cloned Key of Bones which turns back into his hand. But when Lyzera and Varg attempt to make him surrender, Warlock uses his magic to make Lyzera (also magical) and Varg fall to the ground. A wizard named Tom Clarke along with help of an Unenchanted girl named Jazz James was able to force Warlock back through the doorway and Varg then destroyed it with his gun but Warlock say he will use the Chamber of Crowe to get through to the Dayside since Randal (the chamber's guardian) left it.
Warlock is able to get through to the chamber and faces Tom's grandmother Ursula Crowe and Tom's father Michael who attempts to get rid of Warlock by throwing a Egg of Brimstone at him, but it doesn't work and is knocked to the ground by him. Luckily Tom along with Jazz and Randal arrive and Tom creates a tear and sends Warlock through it back to the Neverside before he, Jazz and Randal go through too. After arriving in the Neverside, Warlock starts to use Tom's own magic against him but is distracted by Jazz. Tom is able to get Warlock's attention back to him and is once again has his magic used against him but is able to fight back by using a combination of Magic and Science to destroy Warlock leaving nothing but his clothing behind.