Claerwen was originally a Welsh wizard's wand who was named Mathonwy. Centuries later, Charlie Bone inherits the wand. Charlie finds the wand by traveling into the picture of Skarpo, who is a Welsh wizard, and steals it from him. At one point in the series, Manfred Bloor attempts to destroy the wand by burning it. This results in it turning into a moth. In another point in the series Dagbert Endless captures the moth with an enchanted net made by Dorcas Loom. Claerwen escapes the jar that Dagbert had her in and flies back to Charlie.
The wand allows its user to do magical actions if the command is said in Welsh. The wand will only work if it's user is blood related to Mathonwy.