Corrosive Cantrip
Once on each of your turns, when you deal Acid damage to a creature with a Warmage cantrip, you can cause the acid to erode the target’s defenses. The next time a creature makes an attack roll against the target before the start of your next turn, the target takes a penalty to its AC equal to half your Warmage level (up to a maximum of -5) for that attack.
Sources
Valda’s Spire of Secrets (2024)