D&D 5E (2014) What are some monsters that have interesting abilities but fail spectacularly in lore or appearance?

[Fenris-77]

We need a spell slot monster to even things out.

Me: Take 6 damage and lose 3 spell levels.
Player: Nooooooooooo!
Me: Muhuhahahah! Suck it!!

Or something to that effect. Maybe rust monsters and a spell slot sucking stirge variants.

 

[Wiseblood]

We need a spell slot monster to even things out.

Me: Take 6 damage and lose 3 spell levels.
Player: Nooooooooooo!
Me: Muhuhahahah! Suck it!!

Or something to that effect. Maybe rust monsters and a spell slot sucking stirge variants.

An Eraser Golem