Prelude to Darkness is a classic single-player, turn-based RPG with dark overtones. It takes place in a dying River valley on the verge of civil war, and the player can choose either to join this rebellion or stop it.
Prelude is called a "dark" RPG for a reason: It has a lot of moral choices, lots of "gray" areas. For example, in the first town you arrive in, there's a pregnant girl who was kicked out of her house and the her dad doesn't know the father. You can choose to rat the girl's lover out for 250 drachs, or be compassionate and keep your lips shut.