This changes the game to show a time 5 years after the Oblivion Crisis ended. So completing the main quest would make a lot of sense, but you don't have to. You do need Shivering Isles though. In this time Tamriel is under the control of a being locally called the Wicked One. He commands his generals, The Guardians, who command Shadows. You can become a Dark Seducer, Golden Saint or Dremora. The Wabbajack spell and enchantment Now can summon any creature, even SI ones. You can summon a bodyguard and a sabertooth skeleton. The leveled item list for Upper Class Jewelry now includes bronze, onyx, bloodstone and snakeskin rings. The Guardians are The Mountain Giant, Monster in The Closet, Horseman's Steed and The Horseman. Adds a new sword, The Shadow Blade, with a custom effect similar to Dawnfang's and Duskfang's. Adds two new rings to Rindir's Staffs. Hope you enjoy!

Version 1.1:

Fixes a problem with the portal not appearing, adds a new ring, the Undead Ring, which makes you a part of that faction, adds a new spell, Conjure Iron Bow. The portal is in the Anvil Bay near the painting easel.

1.2

Adds a few dragons to Shadowspire, adds some architecture, a few map markers and new stsffs to Rindirs Staffs. Adds two mountains and a forest to Shadowspire. Enjoy!

Compatibility:

Compatible with Midas Magic Spells of Aurum, Advanced Magic, Advanced Summons, Alternative Start by Robert Evrae, Alexanders Wings, Adense Evil Lair, Gates to Aesgaard, Immersive Health Indication and The Heretics Blade.

Not compatible with: Nothing Yet.
Bugs: None yet.
Tips: 1: Before downloading it would make sense to finish the game, or at least some of it. 2: Daedric quests can give you powerful equipment to battle the Guardians. 3: Instead of immediately attacking the Monster in The Closet after entering, head East. You should find the Horseman. Kill him first for his weapon.

Enjoy!