Base Sigma

On a Cybertron ravaged and near-depopulated by the megalomaniac Megazarak, Base Sigma is the last refuge of a few remaining scraps of Autobot resistance. The forces there are led by Defensor, the last in a long line of Matrix bearers.

Shell Game
Coveting the Matrix, Megazarak hunted for Base Sigma, a search that took him deep within the planet to the chamber where the Oracle was kept, where he fought and killed its guardian, Ultra Trion. Sadly for him, the Oracle he had found was a holographic decoy, and he was left with no more of a clue where Base Sigma was located.