The Triumvirate of Terror consist of Hammerhead, Thunderboot, Pile-Driver and their leader, the Mad Thinker. The Mad Thinker devised a scheme to destroy all the Avengers while their leader, Captain America was away on another assignment. Hammerhead was able to defeat Hawkeye in battle and he became their first prisoner. Goliath and Wasp tracked an SOS signal to an excavation site where they were defeated by Pile-Driver. Scarlet Witch and Quicksilver were defeated by Thunderboot and all five Avengers were strapped to a restraining shaft. Mad Thinker wanted his henchmen to steal all the Avengers' electronic equipment and have it transported back to their headquarters. Mad Thinker was off his calculations and did not anticipate Hercules to arrive at the mansion. Hercules engaged his enemies and managed to free his teammates when he smashed the restraining shaft. The Avengers made quick work of the Mad Thinker and his Triumvirate of Terror.

Creation    

The Triumvirate of Terror  was created by Roy Thomas and Don Heck in 1967 and first appeared in The Avengers # 39.