The Sodden Stronghold is an abandoned stone tower with an unclear history, but its old age is apparent. The tower is located in an isolated section of swampland over a ridge to the west of Matcha Manor. Being built on such moisture-rich soil, the structure has constantly settled over the years since its construction, leaving nearly half of the tower sunk into the ground.
It is here where Mario faces off against the Urchin Amalgamation, a fight which culminates in the kidnapping of Luigi by the forces of the Umbral Deluge.