This expansion to Oblivion is worthwhile, but not mandatory.
Bethesda's 2006 smash hit The Elder Scrolls IV: Oblivion brought us an overwhelming action RPG experience with heaps of content and thoroughly enjoyable sandbox gameplay. While Oblivion was by no means lacking in content, an official expansion came out a year later in the form of Shivering Isles, adding a whole new realm to the Oblivion universe, as well as new quests, items and creatures. It is questionable, though, whether those who already have explored every outcorner of Cyrodiil, the province in which Oblivion takes place, will still have the energy to dedicate themselves to this, gameplay-wise, very conventional expansion pack.
First and foremost, it must be said that the way in which the Shivering Isles expansion is implemented into the main game is commendable. 24 in-game hours after installing Shivering Isles, you will receive a message informing you about the appearance of a strange door on an island in the centre of the province. Upon reaching the island, you will find a portal that leads you to the realm of Sheogorath, the God of Madness, who is in search of a new champion. This means that you can use your trusted Oblivion character instead of having to start a new, separate game, while the possibility to travel between the two worlds allows you to transport items from one realm to the other at any time.
One of the things you'll notice immediately after first entering the new realm is how different the Shivering Isles look in comparison to Cyrodiil. While the latter mostly consisted of dense forests and grass plains scattered with ruins and settlements, Sheogorath's realm has a much more surrealistic, psychedelic feel to it. The Shivering Isles (which is actually just one big island with some peninsular formations) are divided into two zones: Dementia and Mania. Mania is a world full of colour, ancient trees and giant mushrooms, giving this side of the island an appearance akin to Alice in Wonderland. Dementia, on the other hand, is a barren wasteland full of dead trees and swamps cloaked permanently in murk. The personality of the NPCs you'll encounter in the game is reflected by which side of the Shivering Isles they are affiliated with, though at the end of the day, they are all equally void of sanity.
The only character in this twisted world that represents both dimensions is Sheogorath himself. This Daedric deity is the embodiment of the abstractness and otherworldliness that is reflected throughout the entire realm. With morbidly humourous, often longwinded speeches he sends you on a series of missions that compose the game's main questline. These quests get off to a formidable start, as they offer scenarios that we simply hadn't seen in Oblivion. One memorable quest lets you assume the role of executioner as you operate a series of gigantic traps that bestow death and misfortune upon a band of overconfident adventurers. In another quest, the paranoid Duchess of Dementia sends you to town to uncover a plot against her life. In this endeavour, you are accompanied by one of her assistants, who can aid you in retrieving information from reluctant citizens by means of administering electrical shocks.
However, it seems as if the developers have invested all of their creativity into the first half of the main questline and simply ran out of ideas for the remainder of the game. Soon after becoming a duke or duchess at the court of madness, the questline transforms into a tedious series of fetch quests that nearly always consist of exploring a dungeon and obtaining an item that is needed to progress through the mission at hand. The higher emphasis on action in comparison to Oblivion's main quests may serve as a redeeming factor for players with warrior-like characters, and the sneak-freaks who enjoyed crawling through Cyrodiil's caves and dungeons will also be able to derive some satisfactions from these missions, but overall, the second part of Shivering Isles' main questline doesn't seem to offer anything that we hadn't seen in Oblivion already.
It is this sense of familiarity that is the expansion's biggest problem. For beneath all the radical changes in terms of visual design and presentation, Shivering Isles really just offers more of the same. It is only natural that the core gameplay is identical, as Shivering Isles is essentially a component of Oblivion, but Bethesda could have made more of an effort to make the new realm feel truly distinct.
One of my personal biggest issues is the lack of new music. While I praised the soundtrack of Oblivion, its essentially fantastic songs do not seem to gel all that well with this new, abstract world. Some new melodies that would reflect the zaniness of the Shivering Isles would have been more than welcome, all the more because avid players of Oblivion will probably already know all of its themes by heart, increasing the need for something new. A similar sense of disappointment can be derived from the lack of new items. Many of the new weapons and armour are actually just the same items from Oblivion with a few added magical effects. There are some new, useful weapons and pieces of armour to be found, but other than that, you will, for the most part, find weapons that you had probably already obtained during your playthrough of Oblivion.
The combination of a considerable amount of uninspired missions and an abundance of familiar content will not bother hardcore Oblivion fans too much, but it does raise some questions about the value of this add-on. Priced at around €25, Shivering Isles does not offer a whole lot of extra gameplay hours in comparison to Oblivion, and despite its impressive new setting, the gameplay just feels too familiar. Those who are simply looking for more Oblivion-style action will probably appreciate Shivering Isles, especially if they can get it at discount price or as part of the Oblivion GOTY edition. All things considered, though, Shivering Isles is a worthwhile addition to the Oblivion universe, but definitely not a mandatory one.