The most unbalanced monsters for each CR up to 20 (or so)?

[Vedhin]

I'll go take a look at the BoVD...



What is "It's Wet Outside"?

Stormwrack.

Guide to the annoying, semi-common alternate names along this line:

It's Cold Outside=Frostburn
It's Hot Outside=Sandstorm
It's Wet Outside=Stormwrack

And occasionally:
It's Croweded Outside=Cityscape
It's Not Outside=Dungeonscape

The ibrandlin is a contender for CR 5.

The Ephemeral Swarm eats it for breakfast, since the ibrandlin can't hit incorporeal things. Lunch and dinner are unsuspecting adventurers of level 10ish and under. Snack is level 5 adventurers.