Blue mold is a fantasy role-playing game monster. It was first used in the Dungeons and Dragons roleplaying game, but has found its way into video games and fantasy fiction since then.
The blue mold looks like a pile of blue glass with the texture of curdled milk. This particular mold is only common in areas with a lot of magical energy, as that is what the mold actually feeds on. The staple of the blue mold's diet is common magical potions, scrolls, and magical gear that has charges. The mold sucks the magical energy out of them, and then it will grow slightly from the energy it absorbed.
The blue mold is usually found hidden away in a corner, inside a chest, or in some other non-obvious place. They attack from these places, without their prey ever even seeing them. Once a blue mold is found it is as good as dead. They are absolutely trivial to kill once they are located.
Only a fantastic world high in magic could ever evolve any form of magic eating vegetation. Blue molds are always located in the vicinity of one form of magic or another. If you deprive a blue mold of magical energy then it will slowly consume itself until it encounters more magical energy. Unfortunately it takes centuries for a blue mold to shrink down to nothingness, and even a tiny bit of blue mold can eventually grow back into a full sized one. Indeed, even slain blue molds are usually just damaged enough to keep them from actively draining large amounts of magic. Basically, they grow back after you kill them. They usually reproduce simply by having small traces of them carried from one point to another on accident.
After encountering a blue mold it is best to dip all of your equipment in alcohol. This is so you do not inadvertently carry a bit of one with you which will grow to full size while slowly draining the enchantments out of your magical equipment. It doesn't sound like a big deal, but no one wants to lose their Deck of Many Things or Holy Sword because they forgot to clean off all the blue mold from their boots.
The blue mold is especially hazardous to wizards. A hidden blue mold can drain away all of a caster's spells and drain the power from all their magical gear in a matter of minutes. The mage doesn't even have to see the monster. Thankfully the blue mold has no way to physically harm anyone, and is easily killed with fire, alcohol, salt, or acid. It remains a terrible threat because it drains magic silently and without any noticeable effect. You won't realize the spell is gone until you try to cast it. You won't know the potion is bad until you try to drink it.
You can usually detect a blue mold with a detect magic spell, magical sense, or any other ability that allows you to "see" magic. They can be found using these spells even when hidden, as they always radiate magic strongly.
My monster nodes are usually based upon material in the various AD&D rulebooks. But they are my own work, as I often expand the information. In some cases I will blatantly disagree with the source material. None of these nodes are cut and paste. You are free to use my descriptions in any material of your own (even commercial material), as long as I am credited as the source.