This item is obtained through the hotzone quests that are given by Franklin Teek in Planes of Knowledge. He is located outside of the guild lobby.
Quests for levels 20 gives Simple Defiant Armor.
Quests for levels 25-30 gives Rough Defiant Armor.
Quests for levels 35-40 gives Ornate Defiant Armor.
Quests for levels 45-50 gives Flawed Defiant Armor.
Quests for levels 55-60 gives Intricate Defiant Armor.
Quests for levels 65-70 gives Elaborate Defiant Armor.
Quests for levels 75-85 gives Elegant Defiant Armor.