The Exolon Monks were first seen in the ship Dark Aster, where they performed a ritual on Ronan before dressing him up with his attire. They would later oversee the execution of a Nova Corp officer at the hands of Ronan.
Following Nebula's successful theft of the Power Stone and Ronan's betrayal against Thanos, Ronan decides to use the Power Stone to lay waste on Xandar (with the help from Korath and the Sakaaran Mercenaries). To that end, the Exolon Monks were tasked to pilot the Dark Aster as Ronan leads the attack.
However, Star-Lord and the Guardians bring in the Yondu Ravager Clan (led by Yondu Udonta) and the Nova Corps (led by Garthan Saal) to stop the attack. Despite the deaths of many Ravagers, Corpsmen and Sakaarans, Ronan continued on the attack by using the Power Stone to attack the Guardians. Eventually, Rocket Raccoon crashes his ship into the Dark Aster's pilot room, killing all of the Exolon Monks in the process.