Does mind control "you control enchanted creature" means that you can only cast it on a creature that is enchanted?
Does mind control "you control enchanted creature" means that you can only cast it on a creature that is enchanted?
No. Whenever an Aura uses the words "enchanted creature" (or "enchanted land", or whatever), it means "the creature/whatever that this Aura is currently enchanting".
Fluttershy is best pony.
If my Control Magic leaves the battlefield, do I lose control of the Mountain Goat that it was enchanting?
Yup. Control Magic is exactly the same as any other card - once it leaves play it stops taking effect, and if nothing else is giving you control of the Goat, it goes back to whoever controlled it before you enchanted it.
...what is it with you and Mountain Goat, guy? They don't even taste all that good.
Fluttershy is best pony.
Mountain Goat is kinda a joke from back in the day. If memory serves, it was in a top eight world champ deck. The guy included one in his deck (sideboard I think) to get it on the tournament lists - or something like that.