Wild Sling

Talk to Kirik Khal once you complete Amanis Khal's Missing Son quest and let him continue to use his wild magic.

In-game description
"Whenever wild mages congregate, strange things happen. Items take on bizarre properties, and spells by non-wild mages can surge unexpectedly. This sling is an item altered by a large concentration of wild mages.

When a bullet is hurled from the sling, it absorbs wild magical energy, transferring it to the target when the bullet strikes. In addition to being quite painful, the bullet will cause any spell cast by the target in the next round to be affected by a wild surge."