Incursion: Halls of the Goblin King

From developer's website Incursion is a freeware roguelike (meaning a text-map, turn-based computer game featuring character growth, permanent death and an emphasis on strategy and gameplay depth) game based on (but not strictly adherant to) the mechanics of the most popular tabletop roleplaying game of all time, made available under the terms of the Open Game License by their owners. Incursion has much in common with other, much more mature games in the roguelike genre, including Nethack, Angband, ToME, Crawl, ADOM and Rogue. However, the strongest (and currently least visible, though that will change) influence in its design was the less popular roguelike, Omega. Incursion uses the Dungeons & Dragons 3.0 rules. Incursion development has stopped and is succeeded by The Veins of the Earth.