Imperium - ROTS is a relatively new fantasy adventure for Windows Phone that has you battling a host of foes as you search for the crystals of ancient imperators so you can rule the world.
The game has a bit of a RPG approach and may be best described as a Yu-Gi-Oh styled card battle game. You can work your way across the gaming map taking on opponents or take on other gamers with the Online Battle mode. There are over 120 imperators to catch and plenty of attacks to learn and improve upon. I would describe imperators as battle avatars or character that are under your control during combat sequences, much like you would find in the Yu-Gi-Oh or Pokemon type games.
Available for low-memory devices, Imperium - ROTS (short for Rise of the Sun) does make a nice first impression and I can see it being a Windows Phone game to keep you occupied for some time.