When Did Morgoth And Sauron Lose Their Original Forms?

I love tracing the fall of Tolkien's big bads—there’s something almost tragic about how mighty spirits get worn down into shapes we can hate. For Morgoth (originally Melkor), the loss of his original, unmarred form is a long, tragic process that culminates at the end of the First Age. Early on he was one of the Valar, a great angelic being who could take fair forms. But he poured so much of his native power into dominating and remaking Arda that he bound much of himself to the physical world; his corruption of the matter of Arda and his habit of investing power into crafted things gradually twisted his being. The decisive blow comes in the War of Wrath: after the Valar finally defeat him, he is captured, and his body is broken and judged. Tolkien says he was cast out into the Timeless Void, deprived of his place in the world, and in that final stripping he effectively loses any originary, fair shape he once had. You can read the core of this in 'The Silmarillion', where his expulsion and the end of his bodily presence in Arda are described with that grim mythic weight.

Sauron’s trajectory is different and, oddly, more human-scale. He’s a Maia—an angelic junior—who served Morgoth and learned from him. For much of the First and Second Ages he could and did assume fair forms: remember how he came as 'Annatar' to the Elves and coaxed the Rings of Power into being. The turning point for Sauron is the Downfall of Númenor at the end of the Second Age. When Númenor is drowned as a consequence of Arda’s remaking, Sauron’s physical body is destroyed and he is hurled back into Middle-earth as a spirit. After that, Tolkien makes clear in 'Akallabêth' and in various notes that Sauron can no longer present himself as truly beautiful or winning; his power to assume a convincingly fair guise is broken. He can still shape himself, and later appears as a dark lord with terrible presence in the Third Age, but the charm and deceptive beauty he used as Annatar are effectively gone. If you dig into 'Unfinished Tales' and Tolkien’s letters you’ll see further commentary: Morgoth was expelled and ruined as a power in the world, while Sauron, though diminished, remained a potent, willful evil that adapted rather than being wholly annihilated. For me, that contrast—one utterly cast out, the other twisted but persistent—makes their stories haunting in very different ways.

If I had to boil it down in one quick story-telling pitch: Morgoth lost his original form by the end of the First Age, after centuries of corrupting Arda and finally being defeated in the War of Wrath. He was physically broken and cast into the Void, so his angelic Valarin form was effectively gone for good (see 'The Silmarillion').

Sauron, by contrast, kept shapeshifting for longer. He could still appear fair into the Second Age (his guise as 'Annatar' is a famous example), but the turning point was the Downfall of Númenor at the end of the Second Age—his body was destroyed there. After Númenor he no longer had the power to present himself as truly fair; he persisted as a terrible, shadowy presence through the Third Age, but the seductive, beautiful mask was lost (read 'Akallabêth' and related notes for Tolkien’s specifics). It’s a neat contrast: one was driven out utterly, the other was ruined but kept coming back in darker shapes.