Watcher of Realms for Android

The levels are designed as gloomy halls and dungeons with paths along which mobs attack the player. The player must protect the exit from the hall. You can place heroes on the map instead of traditional towers. 

There are not many heroes but they all are drown in a beautiful and high quality manner. They can be upgraded by levels and skills. Unlike most of such games, mobs also don't look like faceless hordes of attacking characters. They are well elaborated inteligent beasts of various kinds. For the killed mobs you can get soul crystals for which you can later summon new heroes.