To obtain the 19. Jellyshrooms quest in Trinity Trigger, speak with the Obstinate Recruit in Urbantheria. For this quest, you’ll need to gather 3 Jellyshroom around the Waterways: Southeast. From Urbantheria, make your way to the southeastern map transition to reach the Waterways: Southeast. In this next area, head to the southeastern map transition. Once in this new area, head to the southwestern corner where you’ll spot 3 shiny objects on the ground.
Make sure to loot all 3 then return to the Obstinate Recruit in Urbantheria to complete the quest. As a reward, you’ll receive Quality Peridot x4, Quality Larimar x4 and Quality Benitoite x4.