Why did Sauron die when the ring was destroyed?

[Ñólendil]

Unstashable, that quote about Sauron has indeed puzzled me for a long time. For that is not what is said in the Lord of the Rings. I suppose it could have happened. In Of the Istari published in Unfinished Tales it says of Saruman's spirit (after death) that it 'went whithersoever it was doomed to go' (a phrase I like). Perhaps the quote from the Silmarillion may offer some clue. But I don't care to dare an explanation!

In any case, it does say in the Silmarillion that he was cast out into the Void. But if you consider what is said in the Ainulindalë and also briefly (I think) in The Beginning of Days, you will find that Arda is but one minute Realm (if important) set amid the vast spaces of Eä, and outside Eä is the Void. So I ask you, how could Melkor have been thrust out into the Void from the Doors of Night on the edge of Aman? Aman is a part of Arda, which is within Eä, and the Void is outside that. Doesn't make sense.

Tolkien explains it though, either the passage in The Silmarillion is an obscure reference of an intervention of Eru, in which Melkor's spirit was extracted from Eä altogether, or else it refers inaccurately to the extrusion of his spirit of Arda only.

Eye of Fangorn, yes Morgoth's Ring is indeed a book. It is Volume X of the History of Middle-earth series, and together with Volume XI (War of the Jewels) chronicles the creation by JRR Tolkien of the Later Silmarillion.

It also contains some texts not intended to be a part of the Silmarillion, but inevitably related.