A character has an obviously evil magical beast as a mount, i.e. a Nightmare. How would one go about disguising it for the populus? Would it be able to activate a Hat of Disguise, for instance?
I want it to be disguised in a way so it will no longer be obviously evil (breathing fire, fiery hooves and manes, eating meat, that kind of stuff). A commoner in your stereotypical fantasy setting should be able to look at it without even considering it could be evil.
I will only accept answers that do not change the type of the creature. For instance, I will not turn it into an undead and cast Disguise Undead. I want to disguise it the way it is.