So... phoenixes. I'll explain their mechanics later in the story when Sol actually finds out about them, but no spoilers!
Also this story will contain characters from Magnus Chase and Kane Chronicles - mainly because they're in the same universe but also because, well... you'll have to wait and see :)
-Wolf
It was quite quickly clear that the Avengers were outnumbered by the Chitauri, but, when one (or few, rather) has the power of a god on their side, it does have some considerable side-effects on the opposing army.
Still, the leviathans were the Avengers' Problem of the Day.
And yet, over all the roaring and shrieking of the Chitauri, and the roaring of the Hulk, a feminine voice could be heard screaming "Woohoo!" as a small orange-and-red blur shot across the sky.
"Stark, get your child under control," Steve said into the comms for what seemed like the thousandth time.
"It's not my fault she's helping," Tony replied.
Natasha couldn't help but laugh.
"You'd need all of SHIELD's best agents just to keep her inside a house when she wants to leave," She told them.
"See, Capsicle? The Triple Imposter knows what's happening!"
The orange blur flew across Clint's line of sight, causing multiple Chitauri to drop from the sky and arrows returned to his quiver.
"She's helping, at least," he commented. "Don't spoil that for us, Cap."
The blur came to a stop above Stark Tower – directly under the portal – and the flames receded to reveal a girl of about fourteen years of age, with auburn hair, bright orange eyes, and two large wings that were slightly brighter than her eyes.
That was Solana 'Sol' Stark; the Phoenix.
"Who's gonna bet that I can go up there?" She said.
"Sol, don't," Natasha said, "You're not going to survive it."
"I didn't say 'go up there and survive it', I said –"
"I know what you said; don't."
"Fine…" she looked to her left, and when she saw a squadron of leviathans, her ADHD kicked in. "Ooo – mine!" she yelled as she swooped towards them.
Natasha let out a long, suffering sigh; the only point in telling her not to do something was to bluff until she got distracted.
The only good thing about the way Sol dealt with the Chitauri – there usually wasn't much left of them to deal with.
"Actually, Sol, could you deal with Loki?" Clint asked. "He's flying around on one of those flying things."
"Imma call 'em speeders, but sure!" Sol cried in joy and flew after said speeder.
As she flew after it, there was a roar of challenge from behind her. She turned in mid-air and threw ten balls of fire at it, causing it to disintegrate as she turned back around and realised that ten seconds had been enough for that damn thing to fly off.
"Fucking bastards…" she muttered, before raising her voice for the comms; "Dad, I'm gonna come join you out at the perimeter."
"Thanks – could really use some help with these – SHIT!" that last word was probably from because of him crashing into a wall.
She made it to the perimeter, where there were a few cohorts of speeders flying past.
She incinerated them all, before turning back to the portal.
She summoned up her energy.
"Here goes," she murmured, as she created a massive fireball in front of her. She pulled heat and oxygen out of the air and pushed it inside the fireball.
"Why is it hotter here all of a sudden?" Clint wondered.
"Yeah, remember Sol's abilities? Namely pyrokinesis?" Tony replied.
"Oooh. So, Sol, what, exactly are you doing?"
"Casting fireball." She said simply.
"Not this again…" Natasha sighed. "Last time she said that she very nearly managed to blow up a few square miles of land."
"Not this time," Sol replied, "this time I have a target."
It took a few minute, but once it was adequately charged, she fired the huge fireball at the portal.
"You guys need help? Cause I think I just blew up about fifty leviathans' worth of Chitauri." Sol offered.
"I think I might need a lift." Clint said.
"On my way."
Sol found him in an office building, surrounded by shards of glass and out of arrows.
She offered him a hand.
"Ready to go again?" she said.
"I don't think that's possible." Clint replied.
And then something came over the comms;
"Guys I can shut this thing down." Natasha said, "Can anybody copy? I can shut the portal down."
"Do it!" Steve said instantly.
"No, wait." Tony argued.
"Stark, these things are still coming!"
"I've got a nuke comin' in, it's gonna blow in less than a minute."
Sol's eyes widened. "In other words, we may have bigger priorities right now."
"Sol, go help your father," Steve commanded.
"Capsicle, I was thinking the same thing," she remarked as she flew off towards where Iron Man was trying to direct a nuclear missile towards the portal.