Mindcore

The Mindcore was the collection of the Skith race's greatest minds and the sum of all Skith knowledge. A portion of the Mindcore was installed around the fusion core on all Skith starships. It advised and supervised the commanders and their subordinates. The Mindcore appeared as a huge column of light with a series of disembodied heads. (COMIC: The First)

Technically the Mindcore was a single entity, with the main concentration kept on the Skith Ownworld and a branch or terminal in each ship connected by a hyperspace link. However, other parts were stationed on the Skith colony worlds. After Ownworld's destruction, one of the colony parts took over as the main part. (COMIC: The Age of Ice)

History
The Skith ship Oppressor One landed in Antarctica in 1915, planning to experiment on the fauna there before cataloguing and obliterating the planet when it was revealed that the Skith were not the first to have been on an expedition to Earth upon the discovery of the Tenth Doctor's TARDIS. The Doctor infiltrated the Mindcore after the Mindcore deemed the expedition a failure, and destroyed the Oppressor One. The Mindcore on the ship retreated back to the Skith Ownworld. (COMIC: The First)

A mysterious force destroyed the Skith Ownworld and the central element of the Mindcore. One of the subsidiary parts on a Skith colony world sent the Oppressor Two to hunt down Doctor so it could develop time travel to combat the force. The Oppressor Two showed up above Sydney in 2010 and successfully captured the Doctor and Majenta Pryce, but a conflict between the Skith Leader of Oppressor One and the Skith General of Oppressor Two allowed the Doctor and UNIT to destroy the ship. (COMIC: The Age of Ice)