I’ve always seen it as a mystery, which contributes to the allure of the game. Maybe it contains the source of power Rudy uses to “come to life.” Hence him saying things like “You don’t want to go down there!” And “You don’t know what’s in there!”

Like here’s how I perceived the game’s theme: Rudy is a sideshow act at a carnival, so lifelike and real, because he is real. But at nighttime, he harnesses some secret power hidden under a trapdoor or hallway to recharge himself. As the player “plays with the clock” he’s slowly discovering Rudy’s secret—which is why as time advances, Rudy becomes increasingly belligerent and restless. Then at night when he’s forced to sleep, you find his secret, or maybe you destroy it, and he screams.

I think things are made vague on purpose to leave a lot of interpretation up to the player.