Sludge

A toxic, reality-warping goo. It thrives in water and warm places.

Core Sludge
Core Sludge is the strain of sludge found on Irk. It has no special properties that distinguish it from other forms of sludge, it seems.

Cosmic Sludge
Cosmic Sludge is an indigo, cosmic-patterned strain of sludge found on Earth. It is the type of sludge Sage is made of.

Stardust
Stardust is a glittering pink strain of sludge that is mostly found in a solid powder form. Pookie uses it.

Wraith Sludge
Wraith sludge is a pearlescent light blue strain of sludge that is commonly used by Meekrob and those aligned with the Wraith.

Learned Sludge
Learned Sludge is a chalky green powder that glows in the dark.

Venom
Vampire venom is apparently a kind of sludge. It's dark red and is used in vampire magic.

Effects on Irkens / Noyings
Most strains of sludge have an intoxicating effect on Irkens and Noyings, though one can be inoculated to resist its more dangerous effects as a smeet. It also tends to "burn" Irkens, though it depends on the strain and water content.

Effects on Humans
Humans are not normally affected by sludge, and can consume many kinds without any problems.

Goo
Goo is a processed food product that Irkens use as the basis for many of their snacks. Sludge is used in some part of its production.

Trivia

 * Sage described sludge as tasting like "raw magic," whatever the hell that's supposed to mean.
 * The Control Brains stated that they have engineered several strains of sludge for organic materials processing.
 * It is implied that sludge is the reason for the Irken fear/dislike of water.[1 ]