A group of mercenaries led by Maxximillian B. Thornblade that worked for the Boneheart during the Greyhawk Wars. At the time Maxximillian was under the effects of the Curse of The YellowSkull during which his soul was claimed and tainted by Iuz. This lead Maxx to slowly move from CN to CE. The group consisted of:
Izek, a suelese battle mage that had been imprisioned via a Sink spell and was revived many years later. He was originally LE and leaning towards LN in his new life that he had made for himself but quickly fell back to his old ways and joined Maxx. He despised the chaotic nature of Maxx’s tactics and gave order and precision to the Fearmasters as the strategist.
Tzilla who was revived as the last living worshipper of the Elemental Gods of Earth and Water (the Mud Gods). Having no where else to go and growing tired of the restrictive life she led living with Jebediah, also agreed to join Maxx and gleefully spread chaos and woe.
Sym the Slayer followed his life-long friend simply out of boredom. After all, he and Maxx have been wreaking havoc all over the Flanaess for decades. Adding a few more to the mix was a change of pace. It also distracted him from thinking about his apparent return from the dead.
The Fearmasters met their demise when they were reunited in the climactic battle in the depths of the ruins to Castle Greyhawk between Iuz and the Iuzbane. S`ym had been replaced with a cambion prince by then but was present on the opposite side with the Iuzbane. All the Fearmasters died. The Iuzbane would have as well but at end of the battle a high celestial deva rescued the Iuz bane from certain death and destruction. No such help arrived for the Fearmasters.