The Skith Leader led the Oppressor One to Antarctica in 1915, with an intent to catalogue the planet Earth's life forms for archiving. While experimenting on the local animals, the ship encountered the Tenth Doctor, Martha Jones, and the Imperial Trans-Antarctic Expedition of Ernest Shackleton. The presence of the Doctor and his TARDIS confirmed that Earth had already been contacted by alien races, so it was no longer pristine enough to be worthy of catalogue. His plan to freeze Earth and transform any remaining sentient life into Skithself, following the failure of the Skith not being the first to come to Earth, was stopped when Shackleton threw the leader off a ledge, and the Doctor, with Shackleton's help, sent the Oppressor One into the sun. (COMIC: The First)
The Skith Leader survived the Oppressor One's destruction, landing in Sydney in 2010. He managed to divert Fanson, a friend of Majenta Pryce, from a passing teleportation beam, and the two agreed to work together. After infiltrating the Sydney UNIT base, the Leader called out to the Skith, who sent the Oppressor Two, under the command of the Skith General. The original plan to trap the Doctor and Majenta proved successful, but the General and the Mindcore had new objectives: take over the Doctor and use him to pilot their new SKARDIS. The General declared the Leader no longer suited for command, and threw him into the ship's fusion core.
However, the Leader was not ready to give up, and clawed his way out of the core before he could be consumed. With his last breath the Leader asked Fanson to save his people from the General's folly, then died and shattered into crystal shards. (COMIC: The Age of Ice)