Wizards of the Coast. Accessed at the Monster Manual III Art Gallery here
[I promised more ooze and, well, you’re gonna get it!]
Arcane Ooze An enormous mass of green
protoplasm surges forth. Veins of light appear along its surface, glowing
briefly before fading away.
Arcane oozes are creatures born of magical pollution, particularly the
wastes left over from magic item creation. Expended reagents, failed
experiments and other effluvia that mix together in magical fields for long
enough can come alive and display a ravenous hunger. Arcane oozes eat magic itself,
siphoning it from the minds of spell casters and extracting it by pounding
magic items to powder. They will dine on any kind of magic, but arcane magic
appears to be a particular favorite.
Being mindless and artificial creatures, arcane oozes have no society
or natural ecology. They patrol endlessly in search of magic auras, and will
completely ignore creatures that lack magic auras unless they are attacked
first. In combat, arcane oozes are single minded and fearless, fighting with no
sense of self-preservation until slain. Intelligent monsters, particularly
those that use spells and hoard magic items, tend to despise arcane oozes. Even
dragons may cooperate with adventurers in order to exterminate these menaces.
The Creature Codex 