The planet Skaro was restored after it was destroyed by the Hand of Omega.
By one account, Skaro was restored by the Emperor of the Restoration Empire, (PROSE: The Restoration Empire [+]Loading...["The Restoration Empire (short story)"]) while a historical account of the universe theorised that the Daleks manipulated the timelines, making it so while Skaro was destroyed, they reconstituted it, effectively erasing the destruction of their home planet from time. (PROSE: The Whoniverse [+]Loading...["The Whoniverse (novel)"])
According to another account, the destruction of Skaro had marked the beginning of the Last Great Time War. Skaro was restored in a "third timeline" following both the original and the timeline created by the Fourth Doctor's interference. It was on this restored Skaro that the Old Master was tried and executed by the Daleks. (PROSE: Whotopia: The Ultimate Guide to the Whoniverse [+]Loading...["Whotopia: The Ultimate Guide to the Whoniverse (reference book)"])