Help! I need a creature!

[Cartigan Mrryl]

Kobolds(CR 1/4) with some kind of poisonous weaponry? THen you could make up whatever ability damage you want.

How low do you want the CR? Because I'd suggest almost ANY basic, pathetic monster (Goblins(CR 1/3), Kobolds(CR 1/4) , Kuo Toa (Cr 2) Gnolls (CR 1).) with poisonous weapons, if you don't want any Semi-Intelligent Races to have weapons in your campaign, just make the Goblins have poisonous claws that deal 1D4 or 1D6... something like that. Sorry, but I tried.

I used both of those in a low-level aberration heavy campaign. My players spent each day with an average of 5 wisdom =P

I'd flip out if that happened to me...

 

[Griogre]

I can top that for low CR

Viper, snake, Tiny, CR 1/3
Monstrous centipede, Tiny CR 1/8
Monstrous scorpion, Tiny CR 1/4
Monstrous spider, tiny

All in MM/SRD

Each has poison that does ability damage. And progressively larger versions for higher CRs.

Twig Blights CR 1/3 are in the MM2 also. I ran a low level forest full of bugs on the way to the dungeon and the characters were always down a few points in various stats, usually dex and str. They really started to *HATE* bugs.