Caleb was a defrocked preacher and misogynistic serial killer who served the First Evil as its leading enforcer during its crusade to end the Slayer line.

In 2002, he was responsible for organizing the Bringers' systematic attacks on the Potential Slayers as well as their respective Watchers. He orchestrated the bombing of the Watchers Council headquarters in England, causing the deaths of its director Quentin Travers and many other members of the Watchers Council. He also orchestrated an attack in the Stockton women’s prison, where he tried to have Faith eliminated by her fellow inmates.

Caleb eventually made his way to Sunnydale and set up camp at the Shadow Valley Vineyards, where the Bringers began to dig in order to find the Slayer Scythe. Due to Caleb's challenge, the Scooby Gang attacked the Vineyard. In the ensuing fight, Caleb murdered two potential Slayers and defeated Buffy, Faith, and Spike. He also managed to gouge out Xander Harris's left eye with his bare hands. Spike knocked him down to rescue Xander and the group was allowed to escape.

Empowered by a new transfusion of power from the First, Caleb had a final duel against Buffy, who managed to kill him with the Slayer Scythe.