Emperor Martinianus

Sextus Marcius Martinianus came to power during the second civil war but originally he started out as a “magister officiorum” in Licinius’ court.
In 324 Licinius and Constantine were once again fighting for power during the second civil war and because Licinius was losing he decided to replace Constantine as Augustus and instead replace him with Martinianus as co-emperor.

Martinianus was sent by Licinius to intercept and attack Constantine as he crossed the Bosporus to arrive in the Dardanelles but was unsuccessful as weeks later Licinius was defeated by Constantine and both Martinianus and Licinius were placed under house arrest with the promise that both their lives would be spared. 6 months later Constantine had them both executed.