Dalek Caan was the second-in-command of the Cult of Skaro and a former Section Leader in the Dalek Military Command. Although he eventually betrayed the Cult leader, Sec, Caan is a visionary in his own right.
Dalek Caan fled the Time War with the rest of the Cult of Skaro in a specially designed Void Ship. Caan emerged from the ship with his allies and helped to unleash the power of the Genesis Ark onto an unsuspecting Earth, slaughtering Humans and Cybermen alike. Despite their successes in battle, their army was destroyed by the Doctor and Caan escaped the battle with his comrades via an Emergency Temporal Shift.
Emerging in 1930s New York, Caan aided Sec in his plan to merge Humans and Daleks. He acted as chief liason between the Cult and the Human contractors in charge of building the Empire State Building, but was critical of the plan to merge Daleks and Humans and ultimately decided that tampering with the Dalek DNA in such a way was contradictory of everything the Daleks stood for. He eventually conspired with Dalek Thay and Dalek Jast to overthrow their leader. When the time was right, Caan wrestled control of the Cult from Sec and decided to wage war against Humanity once more.
Caan linked himself into the Dalek mainframe and became a battle computer of awesome intellect and power. However, the Doctor turned Caan's army against Daleks Thay and Jast, and after a heavy firefight, the two Daleks were destroyed. Since Sec had been killed prior, Caan was left alone. After a conversation with the Doctor, Caan escaped again.
After using an Emergency Temporal Shift, Caan attempted to enter the Time War, which was Timelocked by Dialga. Caan's Passage of Time was shattered and he came face-to-face with a superior being. Unable to comprehend this fact, Caan started to go insane. Seeing him as a way to end the Imperial Daleks' meddling with Time, Dialga allowed Caan into the Time War to rescue Davros. Shortly after he showed Caan the vision of Time, which convinced him the Daleks were actually evil and removed his last vestiges of sanity.
Caan went back to preach Dialga's word, but the Daleks were not willing to listen. Caan modified his approach by setting himself up as a prophet and ranted about their supposed invincibility and unstoppableness, which led to their deaths at the hands of the Reality Bomb - Davros formed such a blind trust of Dalek Caan that he did not even comprehend the fact that Caan was trolling them the whole time. Caan, Davros and all the Daleks apparently perished in the destruction of the Crucible when their whole plan backfired.