Rowan Wood is a something that is used against witches.
This material has properties which are untouchable for witches - making it a perfect weapon to use against them. They cannot touch the wood, and if they do make contact with the material, their power is diminished, and they are made vulnerable.
Use by Spooks
Spooks make good use of this wood, and exploit the vulnerability against witches as a weapon. They construct their iconic staffs out of the rare wood.
On their staffs, they install a metal alloy blade, which they use to defend themselves and attack enemies. Witches are also vulnerable against the alloy blade.
The wood is found in forests, in the County. However, the material is rare.