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