Wild Castle: 3D Offline Game for Android
There are no towers in the game, however, there is a wall and a squad of units defending the wall from waves of enemies. You can level up units and substitute them by advanced ones as you accumulate experience. You also need to develop your city for generation of stronger units.
Heroes are also available, and you can choose from 60 different classes, they can be upgraded by RPG rules. The same applies to weapon upgrades. The game can take place even when the player leaves the game. In this case auto battles take place. The game has special treasures that give certain advantages.