Once a title is unlocked, it can be selected within the Player Status menu. Your selected title is displayed next to your name in menus and during duels.

Title	How to unlock
Alara Champion	Defeat every node on Alara.
Auramancer	Control a creature enchanted with three Auras you own.
Demonic Master	Control five Demons.
Herald of Angels	Have five Angels enter the battlefield under your control during a game.
Innistrad Champion	Defeat every node on Innistrad.
Lord of Leviathans	In a duel, control creatures with a combined power of 50.
Mage of Alabaster	Your favorite color is white.
Mage of Azure	Your favorite color is blue.
Mage of Crimson	Your favorite color is red.
Mage of Jade	Your favorite color is green.
Mage of Onyx	Your favorite color is black.
Master of the Planes	Complete the single-player campaign.
Necromancer	Control thirteen Zombies.
Phantom Mage	Win a game controlling only Illusions.
Puppet Master	Control a creature an opponent owns.
Ravnica Champion	Defeat every node on Ravnica.
Shandalar Champion	Defeat every node on Shandalar.
Sliver Hivelord	Win a game with the Sliver Hive deck.
Spellslinger	In a duel, use spells to deal 20 damage to your opponent.
The Annihilator	Cause an opponent to sacrifice five permanents in a single duel.
Zendikar Champion	Defeat every node on Zendikar.