Battle for Wesnoth by Wesnoth

The Battle for Wesnoth is an open source, turn-based strategy game with a high fantasy theme. Explore the four corners of Irdya in seventeen solo campaigns and dozens of multiplayer maps, taking part in countless adventures as you go.
Stable – This version primarily gets just bug fixes and translation updates. Download this is you want a mostly seamless experience between updates.
Beta – This version gets bug fixes and new features, but things may break between versions. Download this if you want to get the latest changes and won’t be too bothered if something stops working for a bit.