PD--- Thanks--- so, that implies it's something they meant to get back to later, since that's a very odd to detail to drop into his backstory, unless they intended to pursue it later, or unless it was a reference to something in history or literature. I know nothing about literature involving unicorns, since when fantasy includes unicorns I see that as an indication to run the other way. Sorry to those who like unicorns. Just a personal bias that says it's a bit too 'fanciful' for my tastes.
I guess no one knows what they intended to do with this later, since the writers' future intentions are all a matter of rumor, apparently-- from what I've seen on this site, anyway. But maybe someone knows if all this refers to some bit of mythology or literature, or something.