The toxic marsh is spread across a large portion of Central City, covering large chunks of streets, with only the sidewalks remaining safe. In gameplay, touching this substance will damage the player, so it makes it difficult to move through the stage. The player’s best option to traverse these areas is to either use the Hero/Dark Shadow states while crossing the toxic marsh or to use a vehicle to ride over it.
- Sonic Team (15 November 2005). Shadow the Hedgehog. GameCube. Sega. Area/Level: Central City. "Knuckles: You may be able to avoid this toxic march by using a vehicle."
- Sonic Team (15 November 2005). Shadow the Hedgehog. GameCube. Sega. Area/Level: Central City Doom's Eye: "This is a Black Arms contaminant weapon. Be advised to stay clear of it."