Epic Citadel is not a game, but an interactive benchmarking tool for developers to test the scalability of the Unreal Engine 3 on various Android devices.
The castle in Epic Citadel is walkable and you can explore grounds to see the detail of the graphics that the engine is capable of producing. There is also a benchmarking tool that will play various scenes and show the frames per second. The benchmarking option is a good indicator if your device is capable of running games on the Unreal Engine 3.
Epic Citadel is an interesting tool, but does not have long term usability for regular users. Developers will probably like using the tool to test basic benchmarks.
Epic Citadel is a visually impressive tech demo with little other use.