EDIT: I have made a more midrange version of this deck that works better for climbing from rank 5 - legend, found here: http://www.hearthpwn.com/decks/250150-tempo-aggro-mage-rank-5-legend . This deck has successfully finished my climb to legend.
This deck really doesn't need a "full deck writeup"
Seriously it requires about 12 IQ to play, simply mully for low cards / maybe a flamewaker and shit on noobs. Flamewaker + mirror image is a retard combo and the coin is amazing value. Easily reach top 5 - legend no problem with this. Not to mention games are under 5-7 mins unless you write a guide while playing a game like I did, GG WP HAVE FUN BROS, F O R S E N B O Y S, T U C K F R U M P
Sorry I was pretty drunk when I put this together but I'll leave the description as is.
In terms of the mulligan, generally keep Mad Scientist, Mana Wyrm, and Clockwork Gnome. Two Mana Wyrm or Mad Scientist can be okay, but generally you don't want two of the same minion. You most likely don't want two Clockwork Gnomes to start
If you have the coin, keeping Flamewaker, can be a great set up to win the game by turn 5. Turn 3 Flamewaker + coin + Mirror Image is crazy strong. Flamewaker + low cost spells is the reason I run Sorcerer's Apprentice
Keeping Sorcerer's Apprentice can also be very strong if you have low cost spells along with it, and can help you set up a turn 5/6 win.
If you are playing against a matchup where early aggression could be an issue (mech aggro, knife jugglers, animal companions) or annoying early cards (Northshire Cleric or Shade of Naxxramas) then keeping a flamecannon or frostbolt is a good idea.
Feel free to discuss, criticize, and ask questions. I will probably add more to the guide if people are interested.
Thoughts from players:
"Wow, can't believe how quick the results were this deck. Such overpowered, many doge.
Some substitutions should be made depending on your opponents during your play session. For example, this deck can be made into a midrange deck with only a few card switches. Very versatile, generally strong deck against the current meta." -POTATOHEAD12
"This deck is more cancerous than my chat. But potent cancer, like th 420 I smoke." -Forsen, May 14 2015
Please rate up deck so I am inclined to improve guide so any pleb can reach legend with ease!