A while ago on Berk's Grapevine, I said that if Toothless leaves in HTTYD 3, I want it to be for a good reason and I want him to come back years later when Hiccup is an old man, so that Hiccup can spend his last days with his best friend.
This is what I came up with.
(To be read out loud, like you would read a legend, while listening to Stoick's Ship)
Ever so slowly, Hiccup got up from his chair and made his way outside. Yesterday he had turned 60, which was extremely old for a man in those times. No one had expected the Chief to live this long, but he had, and he had had the best life any Viking could have.
Thirty-five years earlier on this day, his best friend had left with all the other dragons for fear of Drago coming back, and life had never been the same. For anyone. But Hiccup still had his beloved wife Astrid, his children and his grandchildren as a family.
Every year on this day, Hiccup walked down to the cove where he had first met Toothless, to remember him. He didn't know if he was even alive, but all he knew was that he was his best friend, his first friend, and he would always be a part of him.
But this time, as Hiccup made his way through the forest, he heard a strange but familiar noise. He couldn't make out what it was, because his hearing wasn't as sharp as it used to be.
As he got closer to the cove, he saw a black shape. It wasn't moving, but it wasn't dead, either. It was simply sitting there, peacefully watching over the cove.
The old man made his way towards it, and immediately thought that he was dreaming.
"Toothless?" he practically croaked in his worn voice.
The black shape turned around, to reveal two playful green eyes. It was him.
Even though he was still as black as night, some of his scales had turned grey from age. He had gained a few more nubs on his chin too. His saddle, still in place on his back, was worn from age and bleached light brown from the sun. His prosthetic tail was torn and dirty, and all the mechanisms Hiccup had made for it were old and rusty.
When Toothless saw his rider, the old puppy inside him came out and he bounded towards Hiccup and nudged him affectionately with his nose as if to say "It's not a dream. I'm here."
(here comes the sad bit – if you haven't been listening to it already, listen to Stoick's Ship while reading it)
The next day, Hiccup Horrendous Haddock the Third, Chief of the Hooligan Tribe of Berk, passed away in his sleep. Everyone had known it was coming, for it was rare for someone to live to the age of 60 in those times.
He was sent out on a burning ship, just like his father had, with his human family and the rest of Berk watching from the beach. But Toothless wasn't there.
He wasn't there because, in that burning ship, there was another shape. Larger than a human, with big black wings and nubs along the sides of his chin. Toothless.
He had known Hiccup's end was coming. He had known it would be soon. So he had left the other dragons and had come to Berk, so that Hiccup could spend his last moments with him, his best friend. And seen as his skin was too old to be fireproof any more, the flames in the ship would affect him like it would affect his rider.
So in the end, no matter how long they had been apart, The Two Alphas passed away together.
Please don't kill me XD I wanted to write something sad but happy at the same time, and this is what I created.
I hope you enjoyed it :)