Davros had a device that could allow him to take over the minds of other beings.
When he was freed from suspended animation onboard a prison station by the Daleks, Davros conspired to destroy them so he could start the Dalek project anew. He used the device to take control of Kiston, a biochemist, a human soldier and a few Daleks. He planned to use his forces to fight the Daleks loyal to the Supreme Dalek that had attacked the station looking for a cure to the Movellan virus. When the station was blown up by Stien and with his forces destroyed, Davros escaped in an escape pod. (TV: Resurrection of the Daleks).