Dross

Dross is one of the environments of chapter 1.5, added in The Binding of Isaac: Repentance.

Dross is an alternative floor to Downpour, differentiating itself from Downpour by having more poop and sewage-themed enemies. Just like in Downpour, Knife Piece 1 can be found on Dross II. Some rooms in this green brick sewage recess have a thin layer of dirtied reflective water on the ground.

Along with the watery floor, many visual effects are employed on this floor, such as:

Random walls might have animated pipes pumping brown sewage onto the floor.
Wet rooms have water distorted light reflections on the walls.
Random water shower points consistently dropping water on the floor in small areas.
Small water droplets randomly fall from the sky, leaving small wet marks that dry over in dry rooms, and don't really visually affect the floor of wet rooms.
The floor underneath the water can be tiled, solid concrete, or grated.
Overhead, light is blocked in 3-4 bar grate, multi-pipe, and diagonal pipe patterns, the remaining light hitting the floor and coloring it a little more yellow.
Downpour Buckets also show up here as well, with the full variant of the bucket being full of poop, instead of full of water.

In Dross, some Rooms may have grates on the walls, expelling a strong water flow. The water flow pushes Isaac and everything else in the Room in one specific direction, usually towards the wall opposing the grates. The flow will hamper your speed if you move against it and speed you up if you move with it.

In addition, Dross floors have the rare chance to spawn Giant Poops, Big Poops that take up 4× the space as regular Poops.

Monsters[ | ]

Entity	ID	Description
Drip	870.0	Quickly rolls around in diagonal directions, dealing contact damage.
Big Corn	217.3	Quickly dashes in random directions, dealing contact damage. Shoots one piece of corn upon death.
Splurt	871.0	Dashes towards Isaac twice and deals contact damage. Spawns 2 Drips upon death.
Cloggy	872.0	Randomly wanders around the room, firing four curved brown shots in the cardinal directions. These shots alternate between rotating clockwise and counterclockwise with each shot.
Fly Trap	873.0	Floats towards Isaac, with 3 Attack Flies circling around it. Coughs up additional Attack Flies and releases gas to launch the Attack Flies outwards.
Gas Dwarf	874.0	Chases Isaac, periodically coughing up gas clouds. On death, fires an explosive shot that can detonate gas clouds it hits.
Poot Mine	875.0	Creates a gas cloud and propels itself away from Isaac when it gets hit non-consecutively. Explodes on death, detonating all the gas clouds it created.
Dump	876.0	Slides toward Isaac, leaving a trail of slippery brown creep. After taking enough damage, its head slides off and quickly bounces around the room and its body spews out brown shots until it empties.
Dump Head	876.1	Quickly slides toward Isaac, leaving a trail of slippery brown creep. Can spawn on its own or be created by a Dump after it takes enough damage.
Small Leech	810.0	Chases Isaac continuously, not stopping at walls. Able to swim over gaps.
Fly	13.0	Hovers in place. Does not deal contact damage and is harmless, but can turn into Pooters if they stay around Poop.
Attack Fly	18.0	Red fly that follows Isaac and deals contact damage.
Eternal Fly	96.0	Invulnerable fly that circles Corny Poop and various monsters. Deals contact damage. Turns into a vulnerable Attack Fly after the object or monster it circles is destroyed.
Ring Fly	222.0	Gathers with any other Ring Flies in the room. These flies orbit around themselves while following Isaac. Deals contact damage.
Dart Fly	256.0	Flies towards Isaac and attempts to predict his movements. Deals contact damage.
Swarm	281.0	Follows Isaac in large, tightly-clustered groups and deals contact damage.
Army Fly	868.0	Chases Isaac, moving along the cardinal directions. Forms a line with other Army Flies in the room. Deals contact damage.
Boom Fly	25.0	Flies across the room in straight diagonal lines, dealing contact damage. Explodes upon death.
Dukie	288.0	Flies around the room diagonally, occasionally spitting out 1-2 Dart Flies.
Tube Worm	244.1	Pops out of the ground in random locations and fires a long-range spray of arcing shots where Isaac will be.
Gaper	10.1	Walks towards Isaac, dealing contact damage. Usually turns into a Pacer or a Gusher upon death.
Frowning Gaper	10.0	Walks towards Isaac, dealing contact damage. They start out with their eyes closed, but when they gain line of sight with Isaac, their eyes open and they permanently move faster. Usually turns into a Pacer or with a small chance a Gusher upon death.
Pacer	11.1	Walks aimlessly around the room.
Gusher	11.0	Walks aimlessly around the room, occasionally firing a short-ranged blood shot.
Bulb	61.5	Flies in erratic, angled movements toward Isaac if his active item has charges; on contact, they drain up to 2 charges, but never deal contact damage. If he has no active item, or no charges, they wander around the room aimlessly.
Wraith	807.0	Walks toward Isaac, dealing contact damage. They are invisible and can only be seen through the reflection they cast in the water, or the ripples they make as they walk.
Blurb	813.0	Walks slowly towards Isaac, dealing contact damage. After taking some damage or getting close to Isaac, it fires a chaotic burst of tears at him and chases him more quickly. Can turn into a Pacer or Gusher upon death.
Bubbles	806.0	Slowly walks towards Isaac, firing back shots upon taking damage. Occasionally farts, which pushes Isaac and adjacent enemies away and creates a chaotic burst of shots. Creates a geyser of water shots upon death.
Sub Horf	812.0	Stationary enemy that spins and fires shots while being moved around or knocked back.
Deep Gaper	811.0	Emerges from the floor once all previous enemies have been killed, then proceeds to chase Isaac. Deals contact damage.
Prey	817.0	Wanders around the room, avoiding Isaac and spawning Small Leeches if he gets close. Spawns 3 Small Leeches upon death.
Henry	837.0	Flushes itself away shortly after Isaac enters the room.

Bosses[ | ]


Clog	Colostomia	Wormwood	Lil Blub

Turdlet

Knife Piece 1[ | ]

Dross II (or Downpour) contains a special area in which Isaac can acquire the Knife Piece 1, one of the key items for accessing the Corpse. Two unique features can be found here:

A White Fire Place that cannot be extinguished. Touching it separates Isaac's body and soul, converting Isaac into The Lost (with Holy Mantle if you have unlocked it as a starting item, as well as your current items) for a brief time. After a room is cleared, the player returns to normal.
- Be warned that even if it has been unlocked for The Lost, the Holy Mantle will not be active until Isaac leaves the room. Taking damage in the same room after touching the white fireplace will be fatal.
- When playing as The Forgotten, The Lost still fights with the bone club, and turning into The Soul is still possible.
- When playing as Azazel, The Lost keeps Azazel's mini-Brimstone attack.
A 1×1 room with a mirror on the icon. There is always a mirror that can't be accessed normally.

The mirror can only be entered as the Lost (or Tainted Forgotten (but not non-tainted The Soul) or Dark Esau-stricken Tainted Jacob, the former of which is allowed to retain their [functional] health), after which it leads Isaac to the Mirrored World, where he can find the Knife Piece 1.

No items or pickups other than Knife Piece 1 will spawn there via level generation (i.e. be present upon the room being loaded/entered). However, the player can still get rewards for clearing rooms or destroying objects.
- Beating the boss room will spawn an item from the boss pool.
- While shops do not usually have items or pickups in them, using or destroying a restock machine will spawn items and pickups from the shop pool to buy.

Once Isaac has the Knife Piece and returns through the mirror back to the real world, he will be converted back to the original character. To acquire Knife Piece 2 and complete the process, be sure to head to the Mines/Ashpit II next.

Trivia[ | ]

Dross may be a reference to the Sewers of Dross from Gish, one of Edmund McMillen's previous games.
- It may also be a reference to Sewers of Dross from The Legend of Bum-bo. Though, this stage might also just be a reference to Gish as well.
Like the Downpour, the Dross has unique recolors of certain enemies. Tube Worms, Blurbs, Sub Horfs, Gapers, Frowning Gapers, Pacers, Gushers, and Small Leeches are recolored to fit the floor, Preys and Bubbles are altered to focus on poop, and Deep Gapers and Wraiths get a different texture entirely.
- Lil Blub and Wormwood are also recolored green to match this floor.
Ocasionally, player can find a rare room that only contains Henry. He will smile at Isaac, then get flushed, instantly getting killed.
"Dross", other than a synonym for rubbish and feces, is the residue of smelting of precious metals, frequently mentioned in the Bible as a methaphor for impurity and worthlessness.

Music[ | ]

The music for the Dross is called Night Soil.
- Night Soil is a historical euphemism for human waste, which used to be collected at night from cesspools and eventually made into a fertilizer.