Both Horde and Alliance can participate, but if an Alliance member wins they will need to make a horde alt to redeem the code in game, cause I don't have any Alliance characters or space left to make one to whisper you in game and give you the code.
Disclaimer: There is a small chance the code is actually for a Tabard of Frost because it's part of 3 codes I found today from a year or so ago when I was redeeming some of these and I am not sure which is for which, but I am almost 90% sure it's a Void one, if it isn't, my apology, the frost one is still cool and just as good.
So yeah. All you need to do is post here, I will randomly draw the name in few days to give everyone a chance to join in on this. Tell your friends if you want and have them post too. I don't get anything out of this, I just wanted to give it away to Boulderfist and figured this is the best way aside from just tossing it in trade chat and randomly choosing someone there.
Good luck and hope you win!
Edit: I am currently wearing a Tabard of the Void if you want to see what it looks like on a character you can view it through my profile.
Edit 2: If you post with different characters just so you can get multiple entries, you will be disqualified. You can't really pull that trick on these forums with the account ignore feature so don't bother trying and hurt your chance to win in process.
Edit 3: Deadline for entries is Saturday August 4th at Midnight server time. The winner will be drawn on Sunday and I will attempt to get in contact with them during that day to pass on the code.