Skardal was a rogue planet.
A collision with Omega Three altered its course to one which would cause it to collide with Skaro. The Daleks altered its course to one away from Skaro and which would cause it to collide with Mechanus. (DC: The Rogue Planet) 2K destroyed Skardal with a Dalek warhead, thus preventing the destruction of Mechanus. (DC: Impasse)
Behind the Scenes
Skardal was spelled Skardel in Impasse.