On a successful hit with a physical ranged weapon (including thrown weapons, but not spells or wholly magical effects), the wielder deals an additional 1 damage as Acid.
Runestones are single use items that are turned in to the coach prior to starting an adventure. The effects get added to your overall stats. One runestone may be used per adventure. However, up to two additional Rare/Ultra Rare runestones can be attached to one weapon (or one runestone each on two different weapons) if the player possesses a Runestone Fitting Base (one per additional runestone) and presents it at the beginning of the adventure with the additional R/UR runestone(s) of choice.