Arc: Twilight of the Spirits is set in a world divided between humans and Deimos, both reliant on Spirit Stones for balance. As the human army seeks to control the Spirit Stones, the Spirits select two heroes, Kharg and Darc, to unite the races against injustice. Kharg, a human noble seeking revenge, and Darc, a Deimos slave aiming to lead his people, must overcome their differences to save the world.

The fourth installment in the Arc the Lad series, Twilight of the Spirits features tactical battles allowing strategic positioning of characters. While primarily a Japanese-style RPG, players can explore towns and dungeons with a small party, alternating between Kharg and Darc. Characters can learn special attacks using accumulated SP in battles.