Arkellis

Arkellis was a rare flower that grew on the planet Skaro. Now extinct, it would only take root in metal. (DWA: The Dalek Book (1964)) The sap from this flower was used to infuse Metalert Dalek casings. Due to the rareness of this substance, only Dalek Sec is known to have used it. (DWF: Birth of a Legend)