Javelin

Javelin is a free open-source single-player role-playing game written in Java that uses d20 as the rule system – also found in Dungeons and Dragons (versions 3.0 and 3.5) and its successor Pathfinder. It draws heavy inspiration from many other video games, from Jagged Alliance and Dungeon Crawl Stone Soup to Pokémon and the Final Fantasy series.

Features

 * True artificial intelligence with easily customizeable thinking time!
 * Uses a d20 (D&D) variant rule system, balancing classic hack-and-slash with a more dynamic turn sequence!
 * A dynamic game world with locations to explore and 6 independent computer factions!
 * Party-based gameplay - control one or more squads, not just a single hero!
 * You choose how to level up your team!
 * In-game help! Either by pressing h or function keys (F1, F2, F3...)! for the game guides.