So I’m fairly certain the only Unicorn in the ES series is the one from Oblivion but who knows. What links him to Skyrim is the fact that he’s involved in a quest given to you by Hircine the Daedric Prince of the hunt. In Skyrim he sends you after a werewolf but that’s not that interesting. The Univorn quest reminds me of Legend with the horn being a desired object, so hircine sends you to kill the Unicorn and take its horn to him and in turn he gives you the Saviours Hide (light armour tunic fur armour), which obviously re-appears in skyrim after you kill the wolf. I feel like the unicorn quest is more interesting: you enter a grove in the Forrest’s of Cyrodil where several Minotaurs defend the grove. If you approach the horse with a drawn weapon the unicorn will be instantly agro’d and will never back down. You can kill the minotaurs using only magic to avoid triggering the Unicorn; as in Oblivion a spell is equipped to you without being wielded like a weapon how it is in Skyrim. Once you ride on the mythical horse it will act as your horse, being sent to stables outside cities etc. The only issue is once triggered it will attack you or guards even if just training as it feels threatened. So doing the quest you can have either a unicorn steed or give the horn to Hircine and get the saviours hide. I believe the Unicorn is faster than most average horses, but not faster than Shadomere: the undead horse who is unkillable.

This was a very basic custom, I was sitting with a foil sweet wrapper and rolling in my fingers into a spike and thought it would make a good base horn so I got another Shadowfax, removed some hair, made a hole, put the foil horn in, sculpted over with miliput, waited 4.5 hours, went over with superglue and then painted. Horn and horseshoes were painted black then silver then gold for a pale gold look. Simple quick, more than likely done by someone else with same base before lol