Marsh Rooms is an unlockable challenge in Benighted Soul, a mod for The Binding of Isaac.

Description:
• Destination: The Duke of Flies
• Character: Tainted Eve
• Starting items:
Golden Key
Sumptorium (Consumable slot)
Yum Heart
The Battery
PHD
Blood Bag x 3
Old Bandage
Little Baggy
Car Battery
Spirit Sword
Birthright
4.5 Volt
Candy Heart
NO! (Smelted)
Red Hook
Circumcision

Yum Heart takes 1 second to use.
(Can be interrupted by hurt)

Starts at final level Corpse with some changes::
• Biggest Map (13x13).
• Starts in room No.0 (The first room).
• Only one route, column by column.
• Treasure Room at each end of column.
• Boss Challenge Room pre Boss Room.
• Boss Room is room No.168, doors open.
• Fake Bed at the middle of the map, which teleports Isaac to room No.0.

Entering Boss Challenge Room for 6 times to skip and spawn a Bed.

Final boss The Duke of Flies is 66x Hp while other enemies are 6x Hp.

Tainted Eve can only spawn 4 blood clots except in Boss Room.

Final boss The Duke of Flies changes:
• Must be the green variant with 66x Hp.
• Attack Fly spawned will be randomly turned into Bulb (90%), Mama Fly (8%) and Sick Boom Fly (2%).

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Bonus on finished:
Benighted Eve can switch the pocket active item between My Fruit and My Fault by entering the starting room, if My Fruit is at max-charge and not used in the current level.

Unlock Benighted Eve.

• Download Benighted Soul from the Steam Workshop.