The Middle Nursefather who raised Ryoshu (Project Moon) and a former Great Brother.
During his Pilgrimage of Loyalty into the Ruins, Matthias secretly killed 2 other Great Siblings in order to claim the Relic Laevatein (Project Moon) for himself, and was banished to the House of Spiders as a result.
Killed by Moses (Project Moon) and Vespa Crabro during the events of Canto 9