At the start of Shivering Isles—the latest expansion for Elder Scrolls IV: Oblivion —the madness only runs skin-deep. You come into the Shivering Isles as a would-be champion, recruited by the demon that runs the place: the "Lord Of Madness," who's shaped his realm after his own split personality. One half, Mania, bursts with wild foliage and brightly colored monsters, while the other half, Dementia, drags you through grim mud and bogs. And most of what you'll do here is weird, nonsensical, and even evil. You'll suffer drug withdrawal, help a peasant with his suicide pact, and torture suspects based on nothing but a hunch. The locals' neuroses start to become your own, and usually you have no choice but to follow them—or just walk away.
The idea that a game could disorient you into doing things that seem like nonsense is incredibly tantalizing, and it makes Shivering Isles smarter and trickier than the original Oblivion. And while it's easy to blow through the main quest and walk out a legend, Shivering Isles offers plenty of disturbing moments, especially if you like to play as a good guy. Luckily for your reputation, Oblivion takes a laissez faire attitude about everything that happens on the Isles—but that actually makes the experience feel less immersive. Whether you feel like a tourist or an inmate is entirely up to you.