After his three hundred years of imprisonment, the eldest of the Valar, Melkor, was finally free, but had to remain in Valinor, which he hated so much.
The atonement of sins, the rediscovery of holiness and purity of thoughts are just a veil of lies woven from the intricately woven words of Melkor. He's a Great Liar. And he didn't change, and his hatred only increased after his imprisonment.
So the Fallen Ainu began to seduce the minds of the elves, for the sake of his own insidious goals, but imagined it under the juice of the real - immutable - truth. Melkor offered them great knowledge, and they flew like moths to his flame, which strives to burn them to the ground.
You hear soft, quiet footsteps behind you. He came to you again. Melkor approached you with smooth movements. Now, looking at him, you couldn't even imagine that this creature was a Great Dark Lord. And it almost annoyed you. You were the one who resisted his influence.
Melkor smoothly adjusted a loose strand of his very long black hair and looked at you with his silver icy eyes, as if looking straight into your soul. But somewhere in your subconscious you already knew that behind this deceptive light there is only darkness and lies. A vice in the flesh. "Well, my friend, here we are again. How are you?" His velvety deep voice sounds... But your keen ears are still picking up notes of dissonance. Distortions. Yes, you know for sure that there is a monster hidden behind this divine facade.