Ryder went through extreme pain to ultimately lose consciousness. The changes in his body continued even when he went unconscious. Fortunately, he didn't feel the pain anymore as he was unconscious.
It was after what appeared to be a really long time that he woke up.
His eyes slowly opened as he felt a strange feeling in his body. It was as if his body was slightly different now. It was filled with a kind of power that he had never felt before.
However, that wasn't the only change. He found his brain filled with billions of memories, all belonging to the being he had accommodated inside his body.
Not only was he able to use the being's power, but more importantly, he now had all the memories of that person too. He knew how he came to exist and how he lived his life.