In the Murkmire Malevolence, Matthew and Devona were contacted by the Golden Vault handler Meera Raheer for a mission that was ultimately called off. Not really understanding what it meant to be a thief, Matthew joined a heist alongside Margaret Pearl, Leilatha Vencaryn, and Rasmus O'Dranith, growing quite close with the team.
After spending a few weeks proselytizing to an extremely confused flock, the group was called to action. They were tasked with returning the Murkmire Stone, secretly an egg containing a vicious creature, to Doctor Cassee Dannel. During a gala at the Cliffsunder Museum of Natural History, they planned to steal the stone by cart, using a Draft Horse named Marx to carry it across town under the guise of "Cliffsunder Party Supplies."
During the period before the heist, Matthew learned that Cliffsunder and much of the rest of the world worshipped his god under a different name, and everything clicked as to why he had experienced such little success in his gospel. He had better luck proselytizing to the guards of the museum, but took it too far, and was kicked out for seeming to be on mushrooms; unknown to Matthew, he forever altered the life of Clarc Pendergilt-Vanth.
At the gala, the mission as a whole went awry for him; the party believed he could fly when they drew up their plans, and he did not tell them otherwise. He ultimately ended up in a dungeon belonging to Caelas Helefir after accidentally making it seem like he worked for his brother Ulre. In exchange for his life, the aarakocra convinced Caelas that he could work for him, and ended up on the payroll of the Helefir family as an unwilling hitman.
With his status compromised and location unknown, Matthew was considered inactive by the Golden Vault.