WHAT IS IT?
The Bicorn is a creature from the mind of Geofry Chaucer himself . It devours kind hearted and devoted husbands ensuring that it is always well fed.
It is incredibly elusive and as it looks like a particularly well fed panther with a human face it needs to be. In addition to burrowing, something that it is extremly good at, it will drop both horns in the same way a lizard will drop its tail.
The counterpart to the Bicorn is the Chichevache who feasts only on obdient wives and is therefore forever starving.  The pair were often to be found carved into church misericords. 
WHERE DO YOU GET IT?
It makes its appearance in the Canturbury Tales so I would suggest that somewhere in Canterbury a trap might be laid with relative ease . After that it would be a matter of time and patience
USING IT IN REAL LIFE:
There are many uses for a beast that eats people but one that dines on a specific kind of person is going to be slightly harder to place. It's best use I think would be as a happiness detector.
Picture the following scene, You're at a party and have run into a friend that you haven't seen for a long time. He tells you that he has gotten married and it's everything that it should be.
However, a slight narrowing of the eyes or a subtle shifting of his head tips you off and you take the opportunity to introduce your pet Bicorn.
If the beast doesn't immedietly leap upon your friend and gobble him up then you can relax for he's obviously not a kind hearted or devoted husband .
USING IT IN WRITING:
It would be easy to say just have it as a monster of the villain or even the ultimate mastermind behind the shenanigans that brought your hero into this whole thing and end it with that.
But as it has a human face it might be able to talk and what wisdom might it grant the right person?
It would have to listen to it's prey a while before deciding whether or not to eat someone so it may be that someone has managed to tame the beasts and has an unrivaled spy network in place. Perhaps a particular Bicorn has plot advancing knowledge and the hero must capture it before it will spill the beans.
MIGHT ONE CONQUER THE WORLD WITH IT?