Forgotten Realms: Demon Stone (2004)

Three adventurers that have met by chance find the Demon Stone, an ancient prison, just as it breaks before their eyes. The contained evil is unleashed and the two wicked spirits of a Githyanki general and a Slaad lord once again threaten the world. You take control of three heroes: Rannek the fighter, Illius the sorcerer, and Zhai the rogue. Each of them has his or her own unique set of spells. Switch between them any time you want, using their abilities to your advantage. As you progress through the game, your heroes gain levels, learn new skills and acquire powerful items. You will need them all to have even the slightest chance of defeating the ancient evil you stand against.