To begin the 33. Misty Marshlands side quest in Trinity Trigger, speak with the Compassionate Old Man next to the inn at Grimgreed. For this quest, you’ll need to seek the marsh’s lost Arma in the Ever-Rainy Road.
From Grimgreed, take the eastern map transition to enter Ever-Rainy Road. Once in this area, take the southwestern map transition to continue deeper into the area. Make your way to the south to trigger a cutscene after crossing a bridge during which you’ll encounter the Fog Monster. This Fog Monster is weak to guns! Take it out then loot the chest it drops to receive a Skill Booster V.
Afterwards, continue east to the map transition. In the next area, you’ll find a cave to the north. Enter it to locate the altar! You’ll receive a staff for Cyan! With you quest complete, report back to the Compassionate Old Man. As a reward, you’ll receive Fleet Feet Recipe IV and Arcane Extract!