Triumvirate

After the (second) death of Straxus, a coalition of leaders calling themselves the Triumvirate seized control of the Decepticons. Their rule was one of arrogant decadence, dominated by gladiatorial fights for their amusement rather than waging war upon the Autobots. Ultimately, their reign ended when they finally pushed the wrong Decepticons around.

What relation they have with Decepticon Imperial Headquarters, Decepticon High Command, or the Decepticon High Council is unknown.

Fiction

Marvel The Transformers comics

Nothing bad can come of this, right?

An unspecified amount of time after the (second) death of Straxus, a triumvirate of Decepticons, ingeniously calling themselves the Triumverate, [sic] came to power as the new rulers of Cybertron. Legonis, Octus, and Seizer ruled together from their palace at the city Helex, sharing a three-seater throne.

As rulers of Cybertron, the Triumverate were too lazy for active aggression against the Autobots. Instead, they spent their time enjoying arena fights between Autobot prisoners and powerful Decepticon warriors (such as Quake), even contemplating pitting Decepticon against Decepticon should they run out of prisoners, rather than going out to get more.

When Straxus-Megatron (it's complicated) arrived on Cybertron with Ravage in tow, he was horrified with the state of things and challenged the Triumverate's rule. Octus baited Megatron, calling him the Decepticon cause's "most celebrated LOONY!"

Legonis shoved Megatron into the area (of the arena), where cannon-boy bashed up a few Decepticons (including Quake, the schmuck) before making a speech about Decepticon values. Realising that they hated not going out and killing Autobots, the Decepticons turned on the Triumverate for being lazy bozos.

The Triggercons shot the Triumverate in the backs, killing them. The Fall and Rise of the Decepticon Empire.

Ask Sideways

When asked for the name of the Autobot known as "Big Red", Sideways mocked you for wanting to know about stupid things and not wanting to know about more evil things such as the savagery of Gladiaron, the rule of the Triumvirate, or the world-devastating rampage of Megazarak. Ask Sideways, 2015/07/04

Beast Wars: Uprising

During the Great War, a triumvirate of warlords seized Helex and governed it in Megatron's absence. They were eventually assassinated by Punch. Trigger Warnings

Notes

• In their original appearance, the Triumvirate was misspelled as "Triumverate". This article is titled using the proper spelling, which we got from the "Ask Sideways" incarnation of Ask Vector Prime.
• Octus (Octavius), Legonis (Lepidus), and Seizer (Caesar) are a parody of (or perhaps tribute to) the ruling Triumvirate of Rome after the death of Julius Caesar.