Linux.com

Battle for Wesnoth is one of the most popular and played turn-based strategy (TBS) games on Linux, if not the most popular. It's a free, open-source community-driven project which has done some amazing improvements since its initial release, in 2003. It comes with wonderful concepts for gameplay, it includes great 2D artwork and music, and more important, it can keep you playing inside a fascinating universe, either online in multiplayer battles or in single-player mode in beautiful campaigns or single-map mode versus AI.