Avernum 2: Crystal Souls is an epic, indie, fantasy role-playing adventure in a unique, massive world. The subterranean land of Avernum is full of strange caves, cunning dungeons, and the alien inhabitants of the underworld. Explore a massive, underground nation of tunnels and caverns, packed with over 100 towns and dungeons. Fight to complete up to three distinct game-winning quests.
Avernum 2: Crystal Souls features:

Epic fantasy adventure with over 50 hours of gameplay. An enormous underworld, with multiple nations and alien cultures.
Rich game system with over 60 spells and battle disciplines and a multitude of beneficial character traits to choose from.
Over 100 towns and dungeons.
Three separate game-winning quests. There are many ways to fight the invaders. Do just one of them or all three!
Unique races and settings make Avernum different from any adventure out there.
Dozens of side quests and hundreds of magical artifacts. 

The story of Avernum 2 is self-contained, and previous experience with Avernum games isn't required.