Freeze Mage is a deck that has been played for years with varying degrees of success, but it has almost always been in the top 1-2 tiers of play. Freeze Mage is almost a strict alter ego to the other variation of Mage decks, being Tempo. Tempo Mage strives to apply a lot of early pressure to the board and snowball off of a few particularly sticky minions, like Mana Wyrm or Flamewaker to pull a crazy amount of value and typically aggro their opponent down.
Freeze Mage, on the other hand, is one of the most late game combo decks that is ran competitively. The idea behind the deck is to stall using things like Ice Block and Ice Barrier and survive until the late game to take him down with a combo. The deck’s board clear options typically include a combination of Blizzard / Frost Nova + Doomsayer, which is typically enough to stop it.
Finally, getting to the late game, Archmage Antonidas is used to generate some Fireballs to kill your opponent with. A good combo is to use Archmage + Frost Nova, assuming you have some other spells in your hand. This way, you can almost guarantee that Archmage survives until the next turn, and you can generate 3-4 Fireballs with it to win the game with. This, combined with a well-timed Alexstrasza can provide your opponent with very few outs from a nasty situation. Even healing often times wont work, as it is spending precious mana to heal yourself and not remove the 8/8 body now present on the board, or Antonidas for that matter.
On ladder, or even in competition sometimes, Freeze Mage hits some bumps along the road. For ladder, the deck often requires a large time commitment, and with the popularity of aggro decks, this simply doesn’t provide for a quick, efficient or overall reliable way to gain ladder points. It also falters pretty hard against Warrior decks, as Control Warrior is one of the hardest counters to Freeze Mage that this game has to offer. Especially with Justicarr Trueheart, even an Alexstrasza combo means that you still have 30+ armor to chew through with Fireballs, and a simple Hero Power each turn will heal your Warrior friend for 4 anyways.