There are more than 160 missions in the original Elder Scrolls IV: Oblivion, but the one everyone remembers is the errand you ran for the Daedric prince Sheogorath, also known as the “Mad God”. Why? Because it starts with a bunch of people in the woods wearing only their underwear, moves on to the planet's stinkiest cheese, and ends with – SPOILER ALERT – a hailstorm of flaming German Shepherds. There were other great missions, but this was the one that everyone talked about and made sure their friends all played.
Thus, when you learn that Shivering Isles, the game’s first full-on expansion pack, takes place in the home realm of that same divine nut-job Sheogorath, it should come as no surprise that this expansion is A) pound-for-pound, the most creative and interesting Oblivion content in existence, and B) a must-buy.
The quest begins when you hear a rumor - incidentally, you don't hear it from a particular person. Just install the expansion and wait a day or two, maybe take a nap - about an odd portal on an island near Bravil. Everyone who goes through it comes back unhinged, if at all. Naturally, you dive right in.
Two things define the Shivering Isles: creativity and duality. Everything here mirrors the double-sided persona of its creator: that of a whimsical, brilliant artist, and that of a psychotic killer. Thus, the northern half is colorful, with trees that always look like it’s fall. The southern half is gray and black, with barren trees sticking out of gloomy marshes.
There are new alchemy ingredients everywhere, including two elements: madness ore and amber, which can both be made into sexy, powerful new armor and weapons. Those will come in handy when vivisecting enemies like psychedelically-hued mantis-ants, frog men and exploding monster skeletons.