Red Slime

Red Slime, also known as Red Liquid, is a gimmick that appears in Shadow the Hedgehog. It is a substance that serve as the Black Arms' main transport system inside the Black Comet and other of their colonies.

Description
The Red Slime is a thick red liquid that are runs along surfaces like some sort of vine. It serves as the primary transport for the members Black Arms species or those that are kin to the Black Arms. When utilizing the Red Slime, the users insert themselves inside the Red Slime and slither through the vine of Red Slime until they reach the end of, which is marked by a Red Slime puddle.

In Shadow the Hedgehog, the player can use the Red Slime to transport Shadow throughout the sections of the Stages. Almost every Stage in Shadow the Hedgehog feature Red Slime for transport. To use the Red Slime in gameplay, the player has to use the Spin Dash when standing close to the end of some Red Slime. However, it is actually not shown whether the Black Arms could use the Red Slime themselves in Shadow the Hedgehog.

Archie Comics
The Red Slime appeared in the Sonic the Hedgehog comic series and its spin-off comics published by Archie Comics. In this media, it is described as an oozing fungus that the Black Arms use for quick transport. However, it is impossible to use unless the user is a Black Arm or at least part of one, like Shadow. Its actual name is unknown, though it is roughly translated to "Conduit Gel". During the Black Arms' first invasion of Mobius, some of it was brought to Prison Island.

When Team Dark–Shadow, Rouge the Bat, and E-123 Omega–along with the Spider Troupe and a Giga Trooper invaded the New Black Comet to destroy it, they hit a dead-end with some Conduit Gel. Shadow then decided to use it to warp to another section of the New Black Comet to scout ahead. Despite Rouge's protest, Shadow utilized the Conduit Gel, only to end in a room filled with Black Arm soldiers. (SU #59)