In the Mercy Thompson universe, the characters are always saying that the fae cannot lie (but that they twist the truth to the maximum)
However, in one book (I don't quite recall which one, it may have been in the Alpha and Omega series) one fae is punished by the dark lords for, essentially, lying about something.
That always bothered me, I thought they had some sort of magical inability to lie, but that bit contradicts it.
It's the only time in the whole series that a fae lies.
So, can they lie but they are forbidden to do so? Are they unable to lie and this particular fae found a loophole or something? Something else?