MMO devs frequently change the exact stats on an item, over the life of a game, to improve game balance, making inclusion of exact item stats in a wiki self-defeating. This is the realm of a database, such as RoM-Welten. Our only concerns are where does it come from, how is it used/useful, and how do I get one?
You can upload an image showing how this item appears in-game when used to File:Portrait - Rune Catapult.jpg. Please remember to crop the image to avoid as much UI and non-relevant game background as possible, and it should be in JPG format. You can override the default name and/or image format using the portraitname field of this template.
When "used", this crossbow creates Runic Thorn ×999 so you need never run out of arrows. This is why many end-game Scouts have this crossbow in their bag even if they do not equip it ALL the time. The Rune War Bow also has this ability. The Runic Thorns remain in your inventory until you use them, log out, or change characters.