Cluthe is a notably dark curse used multiple times by the bullies that SPHEW confronted. Its effect caused cramps in the victim's legs, so intense that they may even rip apart the muscles as Madam Pomfrey (canon) noticed. Daphne managed to convince her it was the aftereffect of using a Road-Running Charm incorrectly, meaning that their effects do appear to look quite similar. Its appearance is described only as a "Dark Bolt". It moves slow enough through the air that Nymphadora Tonks was capable of creating a shield before it struck. It is evidently not powerful enough to penetrate a Prismatic Shield of sufficient strength, but will instead bounce off.