Image: Rebel Wolves / Bandai NamcoOfficial screenshot from Rebel Wolves / Bandai Namco.
Witchcraft Mastery is a day-only Witchcraft perk that makes spells hit harder. It is the main damage upgrade for a hex-focused build.
Every Witchcraft ability deals more damage, and from rank 2 your hexes can add a burst of extra damage on top.
If your days revolve around damage hexes like Burning Blood, yes. If you only use Witchcraft for utility, spend the points elsewhere.
Day only, since Witchcraft stops working at night.