Cloud AU's

God of Death

The Cloud Arcobaleno was as known for as much as he had secrets. That is to say, a lot, as even his name was fake.
Skull De Morte was not his real name, not by a long shot.
The only things that were true, was his race, age, gender and appearance as well as his likes and dislikes.

So what was falsehood?
His name, abilities, character and background. Which would mean the majority of his identity.

For you see, Skull was actually a Korean citizen. He was in fact a civilian, and he had a nice family too. He'd loved them dearly, even when he was separated from them. As for why he parted from them...
It was to find reasons for why he was still needed in this world. For you see, he had a power that this world didn't need, didn't have a use for anymore.
This power belonged to him, and would have been used if things went the way it had millions of times. Which was the world's worst fate - its utter annihilation.

By what? Humans and their nuclear weapons? Climate changes? Meteorite, solar flare?

—No.

The destruction was caused by beings that transcended and sought out to destroy humanity - even Kawahira would be powerless when faced against with them. They consisted of 8 individuals known as the monarchs - Skull being the successor of one of them.

His predecessor was Ashborn, [Monarch of Shadows]  and [King of the Dead]. Bluntly put, his powers allowed him to revive the dead as shadow soldiers who'd serve him faithfully and control over shadows... Darkness itself.

Also, he was the one to beat all the other monarchs, including the strongest among them - Antares, the [Monarch of Destruction] and [King of Dragons].

When they get yeeted into the future-that-wasn't, their job is to stop a new monarch from rising. As their future friends just so happened to find out another monarch might be hiding in the past.
So, while doing their best to get stronger in order to defeat Byakuran -who somehow stole the deceased Monarch of Monstrous humans' power-, Tsuna, his Guardians and Reborn seek for the one known as 'Ashborn'. Though, among their allies, informants and contacts, Skull was the only one not helping the search at all, saying he'd rather like to see what his future would be like.

And seeing as they'd already passed the Arcobaleno Cloud's trial to unlock more power from the Vongola Rings, Reborn hit him with the cow's bazooka.
It came as a slight shock when no replacement for Skull came. He'd already heard how they all died from the Virus but to see the effect so clearly... Reborn was slightly stunned.
Also, Skull could no longer argue for his so-called immortality; the proof was before him.
The infant stuntman was dead.

As for his Skull: the transition would only be for 5min, and he would be exposed to the radiation in that time, so him coming back soon afterwards is what would be for the best.

...He didn't return. Oh, there was the familiar poof and pink smoke they were all familiar with but nobody came back to fill the empty space. Reborn's pacifier didn't glow in response to another Arcobaleno either. Skull didn't return to their time.

It made them wonder; Did the Cloud Arcobaleno succumb to the Anti-Trinisette radiation already or did Byakuran get to him first in those few minutes? Reborn could admit to himself that he wasn't all too eager to find out the answer to that.
The matter of fact was that Skull died on a foolish curiosity and Reborn had pulled the trigger for it to happen.

After passing the rest of the trials just in the nick of time, they're sent back to the future. There, they find another stranger in the base. It was... a dark knight with wings and armor. If one were to describe it, the appearance fit that of a fiction-accurate fallen angel.
He was made of entirely black and purple, his form rippling with either color's smoke.