Be careful with what you put into your mouth.
The Magic horse's bit and bridal is a cursed item encountered by Hellboy and Tom Ferrell in Hellboy: The Crooked Man. Effie Kolb had put this on Tom's father and literally rode him to death.
Tom kept the bit though and when the opportunity presented itself put it on the vile woman as a punishment for her crimes.
Powers and abilities[]
If you put this cursed item on someone then they turn into a horse. Unable to remove it themselves a victim is doomed to chew grass and be ridden until someone removes it. It does seem to translate the victim's emotional outbursts and attempts at speech into a horsey equivalent.