You infuse your weapon with acid, momentarily corroding your opponent's defenses.

Encounter   ✦     Acid, Arcane, Weapon
Standard Action      Melee or Ranged weapon

Target: One creature

Attack: Intelligence vs. AC

Hit: 2[W] + Intelligence modifier acid damage, and the target takes a -2 penalty to AC until the end of your next turn.

Published in Eberron Player's Guide, page(s) 48.