It's a mythological creature, it looks like a white horse with a horn on its forehead. They only approach virgins. People say that unicorns grant wishes to those who are deserving.

[ Ah, the 'unspoken thing'. It's always both fantastic and terrible all at once. ]

That's a good start already. The myths always say that Hades has a 3 headed dogs guarding the Gates of Hell. Do you know if that's true?