Daleks from a parallel universe were summoned by the Dalek Emperor to aid them in conquering Mutter's Spiral. Like the Humanised Daleks, their values were completely different from the Emperor. They sided with the remnants of the Earth Alliance against the Dalek Empire.
Biology
The Mentor's Daleks resembled conventional Daleks in shape, size and style, but they had a different livery. Their voices had a more relaxed tone and human inflections. (AUDIO: Dalek War: Chapter One)
History
They were been created by the Mentor, an angelic being in appearance who was encased in a glowing, golden throne, to be the guardians of peace and order in their own universe, which they ruled in its entirety. (AUDIO: Dalek War: Chapter One)
The Mentor referred to Skaro as the home planet of the Enemy Daleks in the primary universe, suggesting that they may have originated on a different planet in their own universe. (AUDIO: Dalek War: Chapter Three)
Following their arrival in the primary universe, they were appalled by the crimes committed by the "Enemy Daleks" and immediately ordered them "neutralised." (AUDIO: Project Infinity)
After they came through the dimensional rift, the Alliance Daleks, as they came to be known, declared war on the enemy Daleks and fought alongside the Earth Alliance. Within approximately six years, they had driven them back to a small stronghold within the Sol system.
Over time, Kalendorf, Alby Brook and Mirana began to develop doubts about the Mentor and the Alliance Daleks. Reports suggested that they enforced peace and order with the same ruthlessness with which the Daleks from the primary universe subjugate and conquer. Several planets which refused to provide troops to the war effort were reduced to a medieval level, having had their whole industrial infrastructure destroyed. In a more extreme example, Emeron, which had been embroiled in a nuclear war by the time that the Dalek War began, was reduced to a Stone Age level. These worlds came to be known as the Punished Planets. The actions of the Alliance Daleks led Kalendorf to conclude that they had merely swapped one dictatorship for another, outwardly more benign one. (AUDIO: Dalek War: Chapter One)