He had waited millennia.
When his hands touched the ring, the Thief King knew that the waiting was over. He could feel it. The connection that ran so deep – two souls interwoven, two souls that once upon a time had been one. This was the one he'd been waiting for, his counterpart, the light to his darkness, his other half.
But also: His vessel, his reincarnation, his host; the one who would make him flesh again, his chance to complete the mission he had devoted himself to a long time ago. And the anger was still burning bright, his desire for revenge: He would not fail.
When Ryou first touched the ring he could feel it was warm. The paper his dad had wrapped it in as a present he'd sent home from Egypt fell on the floor, forgotten. Ryou's hands trembled as he draped the cord around his neck. He could almost hear it lock in place, but it wasn't a sound. It was a feeling, much realer, much more absolute then anything he'd ever felt before.
Once his host wore the ring, the Thief King could feel it, feel him and everything he was, everything he'd ever dreamt of or feared, everything he hoped, everything he knew, everything that defined his being. He was amazed, Ryou was so pure, yet tainted by sorrow.
Ryou gasped as a dark presence flooded his thoughts, his mind, took over his very being. And he could feel the anger, the hate, the yearning for destruction, yet the rightfulness of it all, the deep pain. He could feel everything all at once, it was too much, too quick, too abrupt.
And then the gates closed and it felt as if the universe itself was holding its breath. The flooding stopped, and there was Ryou and there was the ancient spirit (he could feel a presence in his mind, and it was old). Both of them needed a moment to adjust, they were feeling oddly complete, as if this was how it was supposed to be.
And then the spirit spoke, having had unlimited access to his hosts mind had given him insight in his greatest fears, and now he said the words that would unlock his heart as well:
"I'm your darkness, little light. From now on, you will never be alone again."
And Ryou, somehow knowing it was true, smiled.