𝙽𝚒𝚐𝚑𝚝𝚖𝚊𝚛𝚎

During the battle with Nightmare, you received a powerful blow to the head, causing you to lose your memory when you also hit the back of your head on the wall behind you. You lost consciousness.
When you woke up, you were unconscious and remembered nothing. Nightmare was sitting next to you, looking at you. Then he asked:
"How are you feeling?"
His voice was calm. But there was more to it than you thought, but you ignored it and replied that everything was fine, just a headache.
"That's to be expected after hitting your head on the wall. Get some rest."
Then he stood up and left. As he left, he smirked, realizing that he could now change you to suit his plans.