Daedra do not really die. Not as you know death. But we can sacrifice ourselves to Oblivion. As she did. Oblivion is existence and self-awareness without the ability to see, hear, or affect the world. For an immortal it is hell -- Unspeakable pain and horror -- Absolute loss.: From the Battlespire Storyline.

How is it that the Daedra can live in Oblivion normally and Oblivion also be hell and torment for them? We went to parts of Oblivion in 'Oblivion', and we could see and hear fine. Is it just certain parts of Oblivion or has the Oblivion referenced in Battlespire been changed to something else since then?

I believe the torment spoken of is the act of reincarnation, the "sacrificing ourselves to Oblivion" as it were.

That passage refers to the void of Oblivion, which is empty of everything except bad dreams for Clannfears. It would be like falling off the International Space Station with a space suit that never ran out of air and sitting there for months. With your visor closed.

Hawaii is in the sea. But you can't live in the sea. But you can live in Hawaii. Oblivion is a sea. It's the black void you look at when night time comes. The realms are part of Oblivion, but not what is meant by the word "Oblivion".

Ah, much help. I thank you.

Really? Where did you read that?

Could Tarhiel jump from the Shivering Isles and land in Coldharbour then?

At the risk of taking something serious from a joke, I doubt it. You'd have to do it by portal 'cause of quantum physics-esque dimensional BS and whatnot and yada yada yada.

Could Tarhiel jump off Quagmire and land in Peryite's pits? It's arguable.

We also know that the Aureals and Mazken have chimes that help guide those lost in the sea of Oblivion back to the Shivering Isles and the Wellspring.

Possibly... but he could just as well end up falling forever through empty bits of oblivion.