All this time it’s been missing ;_;
Acid attack applies [Corroded] levels. Much like curse, it penalizes defense pools.
I know! I was amazed that no one ever told you considering it's one of the starting skills! I had a feeling it might be defense-down since there was no defense equivalent to Curse.
(Speaking of, can negative defense levels start adding dice to the attacker's pool or does defense only get reduced to 0?)