Not an actual expansion, but an official plug in which Ты can download to your PC if Ты have the original Oblivion client, and is included in the console versions for Oblivion Game of the год Edition.
Once Ты have the plug-in installed, just wait a few days in game and you'll get a new quest called "Pilgrimage". It will tell Ты about an attack on the Chapel of Dibella in Anvil.
A little trick I like to do when I play Knights of the Nine: because the lore of it requires a worthy knight who is pure of сердце (which means 0 Infamy rating), when Ты complete "Pilgrimage", your character's Infamy rating is reset at 0. I will do all the Thieves Guild and Dark Brotherhood quests, rack up some еще Infamy, then do the Pilgrimage, and my Infamy will be reset, even after all that ^^.
Go to anvil close to the chapel (he will be yelling) is the prophet talk to him blah blah blah and pray to all the wayshrines blah blah blah then i dont no what to do cuz i dont no where all the wayshrines