I know who Tom Bombadil really is
(I once shared this idea with alyssabethancourt and decided that hey, why not, the rest of the world should know.)
So, there are a lot of theories about Tom Bombadil. Nature spirit, avatar of the Secret Fire, personification of music, Aulë in disguise. And we accepted these various theories because they seemed to hold just enough water to be plausible.
But we were all of us deceived.
Mandos prophesied Dagor Dagorath, the Last Battle, when Morgoth will break the Door of Night and return to the world. But he was wrong. Morgoth is already back in the world. Morgoth is Tom Bombadil.
After Morgoth’s defeat at Angband, he was chained and thrown out the Door of Night, into the Timeless Void. Since the Void is Timeless and exists outside of the continuum of Arda, Morgoth’s ultimate punishment was not to simply exist there – it was to be sent back, to the very beginning of the world. Manwë and his fellow Valar, or maybe even Iluvatar himself, broke Morgoth’s already-reeling mind. It was refashioned, repurposed, reshaped, into a harmless woodland spirit nevertheless vested with fantastic power.
Tom Bombadil exists throughout the entire history of the world, keeping to his demesne, never interacting in any significant way with any of the goings-on. His only contribution, his only true mark on the world, is when he saves the Ring-Bearer and by doing so ensures the defeat of his chief lieutenant Sauron.
Dagor Dagorath will come. But it will not be as Mandos prophesied. Morgoth does not need to break the Door of Night. He needs to break the door within his mind, the one sealing away everything he is, buried so deeply that he doesn’t even know it exists.
When Dagor Dagorath begins, the forces of the Valar will hear a song, faint at first, but growing slowly louder as it approaches. And it will go:
Hey dol! merry dol! ring a dong dillo!
Ring a dong! hop along! Fal lal the willow!