Dross

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

Dross is an alternative floor to, differentiating itself from Downpour by having more poop and sewage-themed enemies. Just like in, 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, reflecting almost everything above it, Players, Items Enemies, and Tears.

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 effect 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 remain 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 river will hamper your movement if you try to push against the current, and speed you up if you go with the flow.

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

Monsters
Most monsters on this floor are black, green, and/or yellow, with copied downpour enemies also suitably painted to fit with the theme.


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Knife Piece 1
Downpour II (or Dross II) contains a special area in which Isaac can acquire the, one of the key items for accessing. Two unique features can be found here:
 * A White Fire Place that cannot be extinguished, touching which separates Isaac's body and soul, converting Isaac into (with  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.
 * A 1x1 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 ), after which it leads Isaac to the Mirrored world, where he can find the.
 * No items or pickups will spawn there. However, the player can still get rewards for clearing rooms or destroying objects.

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 and complete the process, be sure to head to / II next.

Trivia

 * The Dross may be a reference to the Sewers of Dross from Gish, one of Edmund McMillen's previous games.
 * The Dross may also be a reference to the Sewers of Dross from The Legend of Bum-bo.
 * Like the Downpour, the Dross has unique recolors of certain enemies. Tube Worms, Blurbs, Bloaties, 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.
 * Ocasionally, player can find a rare room that only contains Henry. He will smile at Isaac, then get flushed, instantly getting killed.