Ok... to get the timeline straight, Infinity War hasn't happened yet. Most of the events of Thor: Ragnarok did not. But, Odin is dead, Loki and Bruce were on Sakaar and have met Valkyrie. Asgard is not destroyed. And the Avengers know that Loki was being controlled in the First Avengers.

Thor knew that something was going to go wrong it was big. Bigger than Ultron and when his brother had first tried to take over Midgard, even though it was discovered that the scepter had control over his mind as well. Something seemed to itch below his skin. A feeling he had begun to have since his father died. Heimdall said that it was the power he inherited when he took over as King of Asgard, a way to tell if your people would be in danger. Thor's fears were confirmed when a mysterious letter was delivered to him at lunch one day at the tower. In front of his teammates and friends.

Thor,

Danger is on the horizon. I'll meet your team in one hour.

Tony was the first to speak up after the letter was passed to the other members. "Who sent this and what do we need them for?"

"He is a very old friend of the royal family of Asgard." Thor said mysteriously.

Checking the time, Thor started to gather all of the Avengers together in the main meeting room. He also called Loki, thinking that he might want to see his friend. He seemed uninterested until Thor mentioned who it was. Loki came over right away.

Once they were all assembled, Thor realized that this must be very big for the Master of Death to be willing to help, the last time he was on Earth, was before Thor was even born. Seeing the anxious looks on the faces of the rest of the team, he started to describe his friend a little, not wanting to give away too much though. "His name is Harrison James Potter, but don't call him anything besides what he tells you to. I once made that mistake. He is one of Asgards closest friends and allies." here he paused, "don't make assumptions, he is a very powerful warrior."

Right as the clock turned two o'clock, a pop was heard behind them and they jumped at the sudden appearance of a tall man in a black cloak. Natasha and Clint right for their weapons. Only to have them jump out of their hands and appear at the feet of their guest.

The man pulled off his cloak to reveal a face framed with dark black curls and high cheekbones. His eyes were what drew everyone's attention, they were bright green with flecks of gold. He wore all black but a strange pendant hung from his neck, an unearthly glow emanating from it.

"Greetings protectors of Earth, I am Harrison. I am here to help. I am quite aware that a group of warriors will be wary of a new player coming onto the field. You all may ask one question and one question only. Including both of you, sons of Odin" At that Loki opened his mouth to respond, but Harrison beat him to it. "I am older than Odin himself. He raised you, did he not? And... you know quite well that though she is not mine and is full grown, I still consider her to be mine own child."

Loki shut his mouth and looked ashamed, much to the brief amusement of Tony Stark.

"Who will ask me first? Loki and Thor, you will be last."

Steven Grant Rogers, Captain America, the man out of time was first. "What exactly are you here to help us with?"

"Ah, getting right to the point. A mad titan named Thanos has decided to attempt to gather the cosmic stones in a bid to gain the favor of Death." Loki and Thor snorted at this, getting weird looks from the Avengers.

Clint Barton a.k.a Hawkeye was next, "You said that you were older than Odin, how old are you then and how do you look so young?" Natasha subtly nodded, agreeing with this question.

"I am older than this universe. I have experienced the comings and goings of way too many civilizations to count." Everyone's eyes opened wider and some mouths did too.

Tony asked, " Why you? Thor told us that you were a friend and ally of Asgard, but why you and no one else, surely someone else could help too."

"Yes, but Thanos has forced me to pick a side. Normally I would stay neutral. By destroying the natural balance of things in the name of Death's favor, he has signed his own death warrant."

Natasha smirked at Harry's answer and asked her own question, "Why has Death's favor got anything to do with this?"

"I am the Master of Death. I will live until the end of time. I am as I said earlier, for lack of a better term, immortal. I exist purely to personify Death. By trying to win my favor by attempting to destroy half of the universe, believing that I would become endeared towards him, he has only made me wish for his death even more than I already did."

It was quiet as everyone thought over his words. Bruce spoke up, "What does that symbol mean, the one on your pendant?"

"Ah… all of you asking brilliant questions. This is what you could call my symbol of power. Called the Deathly Hallows." Tony thought he recognized the name but couldn't remember where he had heard it… so he ignored it for now.

Thor was smiling when it came to be his turn. " Will you spar with me?... It would be a good way to show your skill to the rest of the team."

Harry turned indulgent, "Of course we can but don't expect me to go easy on you like I have every other time."

Loki was the last to ask a question, "How is she?"

Harry smiled, "She is becoming quite the spitfire. And is taking over my past duties quite nicely. She has even found her guide in Garm."

Thor's eyes widened, "Her guide is Garm? I remember when it was just a pup. It sure is a vicious creature."

Tony spoke up once more, "What's a Garm and who is this woman you keep referring to?"

"Ah, ah ah , I said only one question. Now, who's up for some food. I believe that it's getting pretty late."

My other story, 'A Siren's Call' is currently more important to me than this one. It is likely that this will not be updated for a while considering I have very little of it written and my muse is a story hopper, so I write whenever it decides to visit.