Dalek Jast

Dalek Jast was a member of the Cult of Skaro. He had the highest-pitched voice of the members of the Cult.

Origins
Jast was chosen to be part of the Cult of Skaro along with Dalek Thay, Dalek Caan and their leader, Dalek Sec, then went on to begin using their initiative to defeat enemies. (DWF: Birth of a Legend) During the Last Great Time War they managed to escape the carnage by hiding between realities in a Void ship, along with the Genesis Ark, which contained an army of imprisoned Daleks. (DW: Doomsday)

The Battle of Canary Wharf
The Void ship appeared in Torchwood One in 2007, the Cult emerged after an army of five million Cybermen appeared across the world. Jast was the first to realise that the Doctor was still alive after the arrival of the Cybermen when he noticed the Doctor on a video transmission with the Cyber-Leader. During the time in the sphere chamber Jast activated the awakening process and always monitored the Genesis Ark on its priming consoles until the final stage of the awakening (time travellers using their hand to transmit the universe's background radiation as power supply). The Cult needed room for the Ark, and so moved on. During a battle with an army of Cybermen, Preachers and Torchwood soldiers, Jast was overwhelmed with the firepower and shouted "casing impaired" but was later able to reenter the battle with the comment of "firepower restored". During the battle the Genesis Ark rose and unleashed millions of Daleks on the world. Shortly after, the Doctor and Rose were able to suck the Daleks and Cybermen back into the void. (DW: Doomsday) The Cult of Skaro were able to use Emergency Temporal Shift to escape to New York, 1930. (DW: Daleks in Manhattan)

The Final Experiment
Like Caan and Thay, he had doubts about his leader's choices on preserving the Daleks. This showed when Thay protested to Sec about him becoming the first human-Dalek, backing Thay's objections, saying Daleks were supreme and humans were weak. However he assisted nontheless, injecting Sec with Chromatin solution. Along with Caan and Thay, Jast turned against Sec during the creation of the Dalek-humans. When the Doctor discovered the group had overridden th gene feed, Jast took aim at him, ordering him to step away from the controls. Sec ordered Jast to stand down to be met with "He is an enemy of the Daleks, and so are YOU!" After the Doctor escaped to prevent the Gamma strike, Sec protested that the others had betrayed him. Jast replied that it was Sec who had told them to imagine, resulting in them imagining their leader's irrelevance. At the Laurenzi theatre Jast and Thay confronted the Doctor with the imprisoned Dalek Sec. Thay announced it was the begining of a new age. Jast added Earth would become the new Skaro. When the Dalek-humans questioned their orders after Gallifreyan DNA was mixed with theirs, Thay fired on the new Daleks. Jast instantly supported Thay in the battle. Once Thay was destroyed, all the new Daleks concentrated on Jast, resulting in his destruction soon after. (DW: Evolution of the Daleks)

Personality
He had the highest-pitched voice of the members of the Cult. Jast was highly reserved, only speaking when addressed or when he believed it to be vital to the matter at hand. He was a faithfull servant to Dalek Sec and often stayed at his side during their time at the Empire State Building in 1930, until the cult's rebellion against Sec. (DW: Evolution of the Daleks)

Behind the scenes

 * The original shooting script identified Dalek Jast as Dalek Rabe. The Doctor Who Files and Doctor Who: Battles in Time identify him as such.