Lezard and Steff had inadvertently grown a giant
death worm.
All right, they hadn't grown it inadvertently. They'd done that intentionally. What they'd done inadvertently was to give it far too much growth catalyst potion, then allow it to escape Lezard's dorm-room-turned-laboratory.
Now there was a death worm slithering the corridors of Hogwarts, making its way up from the dungeons and roaming the halls at will. Mercifully, it had stopped growing at five feet in length. It was looking for food, to fuel further growth.
(( Wikipedia
describes the death worm thusly: "it is reported to look like the intestine of a cow. It is the subject of a number of extraordinary claims by Mongolian locals -- such as the ability of the worm to spew forth sulfuric acid that, on contact, will turn anything it touches yellow and corroded (which would kill a human), and its purported ability to kill at a distance by means of electric discharge." Since you can't die at Hogwarts, this would make for nasty electric shocks or what have you, but wouldn't be fatal. Feel free to NPC the death worm. Attack it, flee from it, get shocked by it -- whatever you like! In the end, if nothing else avails, we're told the shoggies will eat it.
ETA: apparently the electric discharge is, er,
rectally emitted ...
ETA again: let's say that if you manage to chop the worm in half, you'll end up with two smaller worms. That way some folks can actually defeat a worm without ending the RP for subsequent threads. :) ))