The world of the Shivering Isles also takes on the physical characteristics of the scrambled psyche of the prince. The landscape looks quite different from anything you'll find in Tamriel or Oblivion, and it's all very pretty. From the starry pink skies to the towering phosphorescent mushrooms, there are plenty of great views to admire. But beneath the psychedelic sheen is a world full of monsters waiting to tear you limb from limb. You'll have to fight giant insects, crawling trees, primitive humanoid amphibian creatures, and an entire army of knights known as The Order. Most of the enemies look good, animate well, and put up a respectable challenge in a fight.
To combat all those enemies, you will get new weapons, armor, and spells. If that's not enough, you can make your own weapons and armor by collecting materials and recipes. You can collect amber or madness ore and take it to the blacksmith in Mania or Dementia, respectively. Using the material, you can have the blacksmith forge powerful weapons and armor. The items might not replace your current gear, but at the very least, these forged items will fetch a high price from any merchant. Of course, in addition to forged items, there are plenty of treasures for you to discover in the Shivering Isles' many dungeons. By the time you're ready to leave the Shivering Isles for the greener fields of Tamriel, you'll likely be a very wealthy hero. In addition to the new items, there are a few new magic spells in the expansion, including an amusing spell that lets you summon Chancellor Haskill to ask him for advice.
You'd think the Prince of Madness would be a cool guy, but instead he's just very, very annoying.
Shivering Isles looks fantastic and runs fairly well most of the time, although the stuttering frame rate problem from Oblivion carries over into the expansion as well. On the PC the game also has some stability issues. The game crashed multiple times on two different systems, and locked up one system several times throughout the course of the game.
It will take you a good 20 hours to complete the major quest line, but there's plenty more to do afterward. With all the side quests to complete and territory to explore, you could easily spend 30 or 40 hours or more losing your mind in Shivering Isles, and you'll find that your time there is well spent. The quests, characters, and world in Shivering Isles are all as creative and intriguing as in the rest of the game. Oblivion was huge before, but now it's bigger and better than ever.