Board Thread:Lore Discussion/@comment-71.226.242.68-20131113201112/@comment-24.44.141.89-20131113204906

"As part of the divine contract of creation, the Aedra can be killed. Witness Lorkan and the moons.

The protean Daedra, for whom the rules do not apply, can only be banished."

- Aedra and Daedra

No, they can't be killed. The Aedra's physical forms can be killed but not the Daedric Prince's. Only lesser Daedra can die. To kill a lesser Daedra, you must first kill it's Mundus form on Nirn and then kill it's actual form in Oblivion. I'm not sure if it's possible to destroy their realm as it is infinite. Either way, I don't think that it will kill them, just weaken them.