Base Sigma is an Autobot base from the Universe war.

Base Sigma is the last sanctuary of Autobots on Cybertron in an alternate universe. Defensor, the "Last Autobot" and bearer of the Matrix of Leadership, is presumably based here.


3H Universe comics

Megazarak sought out the Oracle, which was guarded by Ultra Trion, to locate Base Sigma. Seeking ultimate power, he wanted the Matrix for himself and annihilate the Autobot resistance (survived by Defensor) on Cybertron. Shell Game