Let me tell you about how I came to this idea: I recently played the indie video game "Limbo" (SPOILER ALERT) and was very impressed by it. I loved the dark, macabre tone, and the ambiguity at the end when the boy found his sister. It got me to thinking about the Greek myth of Hermes and Persephone, where Hermes enters the Underworld to rescue Persephone from Hades.
I like the idea of a board game where two characters (Hermes and Persephone) are escaping from the underworld, perhaps on a maze-type board. However, obstacles in the Underworld block their path. Hermes can get past some obstacles that Persephone can't, and Persephone can get past some obstacles that Hermes can't. Together they co-operate to escape the Underworld.
two player game where P1 controls both Hermes and Persephone; P2 controls the Underworld and its obstacles.
two player game where P1 controls Hermes, P2 controls Persephone; the Underworld is not controlled by either player but operates through card drawing/dice rolling, etc.
three player game as above but with P3 controlling the Underworld/Hades.
two player game where P1 controls Hermes, P2 controls the Underworld/Hades; neither player has control over Persephone but can influence her movements.
And so on. The game kind of reminds me of ICO from the PS2, where Ico had to look after Yorda in that big old castle. I've played more video games than board games so I think the ideas I have suit video games more, but there you go.
I'd love to hear your thoughts and opinions about this "Persephone" idea. Also, if it reminds you of any board games, or you know any board games with similar-sounding mechanics, I'd like to know!