Well this is simple, ive got an alliance on the PvP realm Dun Modr (spanish) EU and a lvl 1 horde, ill post the screen at the end of this post
First step: you must have a main on a pvp realm lvl 10+
2: Delete that character
3: create another character of the other faction
4: with this new character, you mast contact with a gm and tell him that you wanna take back your main level 10+
5: the gm will tell you that theres no problem with that
6: if the gm is stupid he will give your character back, then, when you noticed that you have your character back fast, logout, and then you have an alliance and horde on the same realm
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