To get a free Deck Key, have a saved game file from Magic: The Gathering - Duels Of The Planeswalkers 2012.
Unlockable Foil Promotionals:
On the player status page, click on the promotions page. From there at the bottom, hit the enter code button. Unlock the following cards by entering the corresponding codes, one card per deck and up to a total of 40 cards for each deck:
CARD - PASSWORD
Promo Unlock 1 - WMKFGC
Promo Unlock 2 - KWPMZW
Promo Unlock 3 - FNMDGP
Promo Unlock 4 - MWTMJP
Promo Unlock 5 - FXGJDW
Promo Unlock 6 - GDZDJC
Promo Unlock 7 - HTRNPW
Promo Unlock 8 - NCTFJN
Promo Unlock 9 - PCNKGR
Promo Unlock 10 - GPCRSX
Beast Within - Win a duel controlling a creature with at least 10 power
Challenge Master - Solve ten challenges
Fearless Explorer - Defeat ten encounters
Flawless - Win a campaign duel with 20 or more life
Last Mage Standing - Win a 3-player, 4-player, or Two-Headed Giant duel
Maelstrom Wanderer - Win a Planechase campaign duel
Master of the Wild Hunt - Win a duel controlling at least ten creatures
Otherworldly Journey - Win a duel online
Praetor Slayer - Solve the Say Your Praetors challenge in all five ways
Savor the Moment - Win a campaign duel with an opponent's library empty
Two-Headed Giant - Win a Two-Headed Giant duel
Archmage - Unlock 30 cards for one deck
Jack of All Trades - Unlock a card for each of ten different decks
Dragon Slayer - Defeat Nicol Bolas in the revenge campaign
"Return To Ravnica" trophies:
Insurrection - Win a duel online using an expansion deck.
Auramancer - Win a duel controlling at least five Auras.
Fury of the Horde - Win a duel controlling at least twenty creatures.
Near-Death Experience - Win a duel with exactly 1 life.
Guildmage - Defeat the Sepulchral Strength deck in the revenge campaign.