Apotheosis of a Mad God file

Extract the archive and copy the DaedricPrincesApotheosis.esp to your Oblivion's Data folder (C:\Program Files (x86)\GOG Galaxy\Games\Elder Scrolls IV: Oblivion\Data\). Check the ESP plugin you just downloaded under "Data Files" in the Oblivion Launcher menu.

The plugin is dependent on the Shivering Isles DLC.

Can be installed 'from day one'; in other words, along with first-time playthroughs. You will only receive such sizeable daedric power after stopping the Greymarch and taking over the Shivering Isles.

Should be compatible with any console or platform the game was released on (PC/PS3/XBox 360) as long as your version supports modding.

Does not require OBSE or anything other than the base game and the aforementioned downloadable content.

Speak with Haskill after fighting the Prince of Order so oblivion can “grant considerable power to its new master”. If you already completed the expansion, just load your most recent save.