Board Thread:Lore Discussion/@comment-25196161-20140718180949/@comment-5989209-20140719034703

The Aedra are never implied to be weaker than the Daedra. It is only that they gave up their power and require worship to still function. They are still pretty damn powerful. Alduin is the one who created Mehrunes Dagon. Lore-wise he consumes the entire planet of Nirn and eats spirits and souls to grow stronger. It's implied that he is weakened in Skyrim only because he was slacking off in his duties.