Davros had a device that could allow him to take over the minds of other beings.
History[]
When Davros was freed from suspended animation onboard a prison station by the Daleks, he conspired to destroy them so he could start the Dalek project anew.
Davros used the device, produced from a secret compartment on his travel chair's control panel, to take control of a engineer named Kiston; a human soldier, a biochemist and two 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 found himself infected by the Movellan virus but managed to get away in an escape pod. (TV: Resurrection of the Daleks)