Download Battle for Wesnoth
This 3D game uses a turn-based strategy mode and has a nice fantasy theme. You will be able to access a lot of races, each having unique units, building and more. You can also add a lot of mods and add-ons to the game, either official or fan-made. Custom campaigns are also something that can be added to the game.
You will have to recruit soldiers and afterwards train them in order to create a powerful army. Your aim is to regain the lost throne of Wesnoth. However, this is not the only ultimate option that you can choose in order to finish the game, thus the replay ability is greater for this game.