Your sigil imbues a weapon or an implement with arcane acid.

Daily   ✦     Acid, Arcane
Minor Action      Melee touch

Target: One weapon

Effect: Until the end of the encounter, any attack that uses the target as a weapon deals ongoing 5 acid damage (save ends).
As a free action, the target's wielder can end the effect when he or she hits a creature using the target in order to give that creature a penalty to AC equal to your Constitution modifier (save ends).

Published in Eberron Player's Guide, page(s) 49.