New Headcanon · 10:06am Sep 23rd, 2014
1. Friendship is Magic.
2. Day-active friends allow use or enhance use of Light magic.
3. Night-active friends allow use of enhance use of Dark magic.
Luna was in first the only night active one, who had only one friend: her sister. Therefore only they both could use Dark magic for a long time, which became therefore known to the common folk as Alicorn magic (Zecora & Trixies amulet), because no unicorn could replicate it. Even Starswil didn't know about this friendship factor of magic.
Pre-alicorn Twilight was able to do dark magic, because she was a friend to Luna.
Sombra was also able to do it, because he was a "friend" to pre-Nightmare Luna. He got on her side, after nobody respected his work with crystals, got "influenced" by the power of Nightmare Moon and finally snapped after her banishment. He also got "banished" shortly after.
With both publicly known wielders of Dark magic, described as fanatics, Dark magic also got a bad repute. While being in "reality" just another form of magic with a different mana source(s). (Friends are mana sources, the wielder counts too)
The Alicorn Amulett was an old token of friendship from Luna. It send Trixie on a power trip which caused her "bad" behavior.
Perhaps I could make a alternative universe fanfic out of that where we see Luna plotting to fight Celestia, befriend Sombra, fall under the influence of the Nightmare and then get both banished at the end. Only plot hole I can see at the moment is the other two types of magic: Love magic from Cadence and the Changelings and Discords chaos magic.
