Here is the full list of all 12 The Keeper of 4 Elements trophies - there are 7 bronze, 4 silver and 1 gold.
Defeat 30000 enemies
Build 1500 towers
Play the game for 8 hours
Defeat 2500 enemies with the Monk
Complete all levels on hard difficulty
Fully upgrade 130 towers
Defeat 300 enemies with the Monk
Sell 10 towers
Build 30 towers
Defeat 100 enemies
Complete a level with 20 lives
Launch all the waves on one map manually