Re: Unicorn Horns and Diamonds(Xbox 360)
There are no unicorns. There are only unicorn horns as alchemy reagents. Long ago, I modded my game so that necromancer merchants (who specialize in alchemy) also sell alchemy reagents. Also, I set it so that chest could randomly contain some alchemy reagents, although these are uncommon.
That was so long ago, I don't even remember how alchemy reagents are acquired in the base game, except those that are picked as plants or collected from creatures. Since there are no unicorns that can be killed in the game, I really don't know how one would acquire a unicorn horn. They're very rare and very powerful, but I'm fairly certain that there's no reason why the player would be limited to one.
As to the diamonds, I seem to recall the dungeon under one of the cities has at least one diamond in it. There's even a quest involving an astrologer and an astronomer, where one needs you to go into the dungeons to retrieve one. I don't remember which one asks for it though.
Alas, that's the trouble with modding one's game. Before long it's difficult to remember how the unmodded game actually works.
"Streamlining is awesome... if you're developing something which needs to be aerodynamic - like a car or a plane. Otherwise, it sucks." - me