I know of two things that can see everything that the person had been through with a person's consent (sort of…) – the sorting hat and Gemini. And because we all know that Natsu is (SPOILER TO CHAPTER 400+) E.N.D, I wanted to see how those two react. Well, the sorting hat would have two situations – one with END in a seal that prevent said hat from entering. The second is that seal is only stopping END from out but lets the hat 'converse' with him.
On with the story…
The Sorting Hat
Situation number one-
The Sorting Hat was placed on Natsu's head (A/N: no plot here, sorry). At first, the hat saw what it had expected when it saw the mage – brashness, loyalty, openness, bravery and some innocence that slightly surprised the boy when the hat mentioned that to him. But before the hat called its decision, it felt its magic touch some kind of a mental wall. That was surprising, it thought, the boy seemed very open and all the memories except the ones before the dragon, Igneel, had found him seemed to be in place. It probably was a very tough time and that's why they are concealed, so the hat didn't too much of it as it faced the wall and end a tendril of–
'Are you finished?' Came a slightly impatient tone from the pinkette. The hat decided that it would tell Dumbledore about it later and announced its decision (A/N: doesn't matter which house). The mage thrust his fists up and went to his new house, leaving behind an intrigued hat.
Situation number two-
The Sorting Hat was placed on Natsu's head. At the first few moments, the hat saw what it had expected when it saw the mage – brashness, loyalty, openness, bravery and some innocence that slightly surprised the boy when the hat mentioned that to him. But suddenly a shiver ran through it, surprising the hat since it should not have those emotions. A dark fog came from deep, deep inside Natsu's subconscious. The malice it emitted jarred the hat that was unused for that kind of darkness since kids should never have those kinds of emotions. Never in his entire existence had come across such a dark being, especially hiding underneath the light that the boy emitted. The fog started forming into a man with dark spiraling tattoos moving across his skin. Long dark salmon bangs slightly covered shinning red eyes and the rest of the hair rested on his shoulders. He was bare and the hat saw a big gaping hole in his chest, where the heart should have been.
Who are you? Thought the hat. The man looked up and flashed a black toothed dark smirk. I am the end for any hope. I am the only demon capable of destroying Zeref and the last you'll ever see. I am E.N.D, he said as he reached for the terrified hat. The tattooed hand was a string of hair away when an annoyed voice yanked its consciousness out and back to reality. The hat could only look down at the seemingly innocent pinkette that was poking the hat impatiently.
"Are you finished already?" The voice of the boy jarred it back to attention and he shakily called out the mage's new house (A/N: again, not important), eternally glad when it was plucked off and was placed away from the cheery pinkette. He must report this to Dumbledore the minute the ceremony ended.
He was not looking forward to this year.
And there you have it, the Sorting Hat's reactions to END. Now time for Gemini's, yay!