For $30 you can now change from Horde to Alliance or Alliance to Horde. I think we all know which transfer might happen a bit more often. If you decide to make the switch, all your equipment will make the move with you and you will be able to choose from applicable races. You’ll have to wait another 60 days after changing factions before being eligible again.
You must be at least level 10 in order to make the change. Unless you’re around the level 40-50 range, I wouldn’t suggest it because of the ease you can get to those levels now.
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