These creatures, which include werewolves, orcs, and trolls, always follow the same path, so your objective is to build your defensive towers along that route to try to destroy them before they reach your castle.
You'll be able to construct any of more than a dozen different types of towers, which you can then upgrade with the money that you earn from killing monsters.
Royal Defense includes two campaigns with different settings, each with twenty missions. If that weren't enough, you also have three levels of difficulty to choose from.
Royal Defense is an entertaining real time strategy game with polished graphics - and did we mention it's free? It's an excellent tower defense game for all ages.