Constraints, or: One Sentence Monsters

Constraints help in generating, because it forces your brain to go places you never intended, because dealing with the constraint engages your brain at a slant. The One Page Dungeon and One Page City are evidence of this. But I just had a thought, one page isn't much of a constraint for an encounter, religion, or monster. Why not One Paragraph Gods, or One Paragraph encounters. Okay, it could work, in fact a lot of blog posts are this already, so it might not be much of a constraint. Let's push the constraints up a notch, One Sentence Monsters. I figure if you can't get the concept across in a sentence it's probably too fiddly or complex. Here are a few classic monsters rendered in one sentence:

Humanoids with squid-like heads and great mental powers that hunger for your brain.

A floating sphere with many eyes on stalks, each shooting different dangerous effects.

That captures them fairly well doesn't it? Okay, how about some of my own deadly distractions:

It appears to be a child when encountered, but will wail loudly if unfed and age decades if fed.

It appears to be a small treasure but if you put it in your pack it will digest your real treasures.

I like this, because now that I think about it, it leaves the nitty gritty up to the DM to determine. I mean, do you really need to have the beholder's eye powers spelled out completely? Would it be less a monster if it had 3 stalks or 18? The incarnations different DMs come up with could be like different species of the original conception.

One sentence is too abstract for a dungeon or city, but I think it might be better for monsters and magic items. So here is my

One Sentence Challenge: Monster! In one sentence, relay a monster that will be intriguing enough that we'd want to use it in our campaigns. Post in the comments.