Marv is the quaternary antagonist in the first half of Duo-Franchise: Carnaval Style. Specifically, he serves as the sequel hook for In Too Deep, a false lead in Summer Edition 2 and the quaternary antagonist in the third act but later turns into a supporting protagonist in the fourth and fifth act.
=In Too Deep
He first appears in the finale. Despite appearing near the end, he made his debut by going after Zachary and emerging from his shell in the process.
Summer Edition 2
The Figure may not have been shown in the arcs but he is mentioned throughout the season.