It seems as if Dagon still has some power though, but this is limited to his shrines as he is able to send (deploy? lol) Dremora from his shrine in Skyrim. You can also just go back to the Shrine of Mehrunes Dagon every few days, two Dremora spawn outside the shrine, and two spawn inside the shrine. I cant imagine that he isnt trying to find some way to return to Mundas though, but youre right, he's pretty much stuck in Oblivion. Oh crap! youre right! I forgot about that detail (pretty huge detail too). He has not attempted to return physically to Tamriel in the 4E because he simply cannot and will-not. During the Dagon Shrine quest, Ruma Camoran will require you to kill Jeelius in a sacrificial ceremony to show your devotion to Mehrunes Dagon, stating. Once a servant of Mehrunes Dagon Lord of Destruction you were one of Dagon strongest Daedric Warrior but forced to betray him after the Dragonborn summoned you for the Sigil Stone you fought the Dragonborn but failed when he defeated you three times you submit forced to seal Dagons Sigil Stone after you gave it to the Dragonborn Mehrunes Dagon summon you. Dagon is absolutely enraged in fury, he will never be able to physically return to Tamriel ever again, however this does not mean his very being was removed from Tamriel, as he can still dominate followers of his cult via his shrines. Yes, even without a Dragonborn Septim Emporer w/ the Amulet & Lit Dragonfires on the Throne. No person ever again will have to fear the manifestation of Oblivion Gates ever re-opening. Players will have to explore the far reaches of Skyrim to find all three pieces and, with the help of Mehrunes Dagon, reforge the blade. It can be obtained from the Pieces of the Past quest.

Originally posted by Strider:You are forgetting Dagon's entire realm of 'Oblivion' are entirely banished from Mundus forever because of Martin's usage of the Amulet of Kings! Which hopefully should give you some closure. That second trait belongs to MehrunesвЂ™ Razor, arguably one of the best daggers in Skyrim.

How to get to shrine of mehrunes dagon