The Arrangement CH 1, Thor+Loki, Thor+Jane
As the latest concrete-eating, giant wurm burst through New York's Bleecker Street, Tony thanked his own genius for including jet boots, because damn, it would suck to be on the ground right now. The rest of the Avengers, unfortunately, were having a harder time of it.
Hawkeye had scaled a second-hand music shop and was firing incendiary arrows while Captain America and Black Widow guarded his position below and tried to not get eaten. The beasts were controlled by a giant gorilla-like alien made of sand that Thor and the Hulk were fighting, but every blow they struck caused the sand to blow apart and reform without injury. Tony's job was to keep everyone alive, mostly by firing rockets everywhere.
The Hulk smashed into the sand creature, scattering half of its body across the street like a temporary beach. Instead of reforming, the sand rose up around Thor's ankles and thighs like a vise. The norse god struggled against the growing binding before starting to spin Mjölnir in preparation of flight. The remaining half of the creature lurched forward, and with one, long swing of its arm, sent Thor flying through a bistro, the building behind it, and out into the street beyond.
"Okay there, big guy?" Tony flew higher to get a better angle to cover Thor from the fighting below. Thor grunted, rolling sideways, and Tony realized the sand trapping his legs was still clinging to him and had bound his knees together. Iron Man flipped his communicator to 'all channels.' "Hey, guys, I've gotta go help Thor get rid of some sand in uncomfortable places."
All of the wurms had come through on Bleecker Street in what Tony could only conclude was stand-up comedy vendetta, so he figured he should be forgiven for only thinking about the danger coming from directly blow.
The two wurms that burst through on Bond Street, rushing Thor from both sides, sent a nasty swoop of adrenaline through Tony. Tony fired a gauntlet of rockets at one, shredding it and the storefront behind it, but his angle meant that the same treatment for the other wurm would rip the thing apart and go right on into Thor. His jet boots flared to full power as he tried to maneuver for a clear shot when a kid appeared between Thor and the charging wurm.
The kid held up his hand, palm flat, and a giant spear of ice ripped through the wurm's open mouth and out its back. The kid turned on Thor, crouching down at his side, and Tony rushed as fast as he could to get down there.
"Back away, kid," he ordered as he touched down. He set the repulsor rays in his gloves to only a low-level stun, but he wasn't looking forward to firing on a kid, regardless. The kid gave him a disdainful look and set his hand on Thor's hip, challenging. Tony gritted his teeth.
"Do not touch him, Stark," Thor ordered.
The kid's hands moved down Thor's legs and in their wake, ice swallowed the sand. After punching the ice around his hips to pieces, Thor sat up and used his strength to crack the popsicle coating his legs and pull it off. The kid's hands were blue-skinned. That and his armor made it pretty obvious he was another inter-dimensional traveller from Asgard.
"Are you all right?" the kid murmured, hands resting on Thor's ankles even after ice had fully coated his boots. Thor reached out and ran a hand through the kid's black hair.
"You should not be here, Loki." He slide his hand down to cup the boy's cheek. "It's too dangerous."
Loki scowled. "I swore to face all dangers with you. Do not make light of my vows."
Thor sighed, and Tony decided to help him out and be the bad guy here. "Sorry, kiddo, we've got strict rules on Earth regarding child labor laws. No one under sixteen allowed to fight intergalactic evil. Between sixteen and eighteen, you're allowed to fight super-villainy for ten hours a week with proper adult supervision, but you've got a little growing to do, so. Either you get out of here, or we're going to have to escort you to safety."
The kid crossed his arms over his chest. "Don't condescend me. Neither of those things will happen because Thor and I are going to kill that scarlak. Together."
"Loki, will you please consider leaving? I would be greatly relieved to know you are safe."
"And what about me?" Loki turned his indignation on Thor. "How am I supposed to stand by and watch you throw yourself into a danger you cannot defeat?"
"Where the hell are you guys?" Black Widow called over the com.
"Sorry, problem with a kid. Be there in a sec."
"There's a child here?" Tony could practically here Captain America's mind grinding away to form a plan to get some hypothetical innocent child to safety. Hypothetical, because there certainly weren't any here.
"Not a problem, Cap. Focus on your own fight." He flipped back on the outside speakers. "Okay, kid--"
"Loki."
"Loki. Right. Here's the deal. We don't have time to waste, so how 'bout you tell us what plan you think you've come up with?" So we can shoot it down and get back to work.
"I am going to use this." He clasped his hands together and when he pulled them apart, there was a box between his palms.
"The Cask of Ancient Winters." Thor looked astonished. "How do you have it?"
"It is mine," Loki said, peevish. "And the Queen Mother suggested I take it to protect myself."
"Okay, kid, I'm sure that box is really important to you, but we don't have time--"
"Nay, Stark. The casket is an extremely powerful tool. I'm afraid we would be fools to turn down Loki's assistance." Thor looked frustrated, but Loki beamed, all sulkiness evaporating. Tony thought he looked more childlike than ever.
They really didn't have time to argue, so the trio ran through the breaches in the buildings created by Thor's trajectory. On the other side, Bleecker Street was more holes than road, and they got there just in time to see the sand creature throw the Hulk down one of them.
Loki darted out, opening the box. Bright light spilled out over the kid's hands, and a shrieking wind rose, funneled by the buildings. The sand alien turned, but ice was already racing to form a thick crust on the asphalt. One step, and the ice settled lightly like a second skin. Two steps, and there would be no more, because the creature was frozen in place.
The kid had also turned fully blue, which, weird side effect, but not something Tony could really focus on because it wasn't over yet. He could see the sand writhing beneath the ice, looking for a new form to escape in.
"Thor!" Loki shouted above the wind. "I've left a small opening at the top of his head and the bottom of his left foot." Thor whirled Mjölnir, and the skies darkened with rain-heavy clouds. "Do you see it?" Loki called, and Thor nodded, grinning.
Lightning struck, blinding, the thunder loud enough to temporarily deafen. Tony blinked dark spots from his eyes and saw the sand wasn't moving because it was gone. All that was left under the ice was glass. With a roar, Thor launched himself at the new sculpture and swung Mjölnir down. A few good smashes and the thing was only a pile of shards.
He turned, jubilant. "Loki--" The smile slid off his face. "Loki!"
Tony pivoted to find the kid had wandered over to one of the holes and seemed to be trying to climb in while cradling the magic ice box in one hand. Thor raced over and scooped the kid up with one hand.
"Thor, put me down! I'm not a child anymore." Loki squirmed in his grip, but Tony noticed that the kid made the box vanish and threw his arms around Thor's neck anyway.
"You cannot wander off--"
"I wasn't wandering. I was going to freeze those Argothian wurms and finish this battle!"
"The Cask of Ancient Winters does not make you invincible, Loki. You must stay where I can protect you." Thor attached Mjölnir to his belt and raised his hand to Loki's cheek. Under his fingertips, the kid's skin paled and the lighter coloring spread out over his face.
Loki turned his cheek further into Thor's palm and looked down, pouting. "Don't be mad." Thor sighed.
"Hey, Stark, where'd you pick up a Smurf?" Clint asked. Tony turned to find the trio picking their way across the swiss cheese landscape.
"What happened to the overgrown worms?"
"Only two left, and Hulk's having fun." There was a roar, and half a worm and the Hulk popped up through a hole. "One more, buddy!" Clint called, holding one finger up high. The Hulk gave a grunt and disappeared back into the ground.
"Hello," Captain America introduced himself to the kid, offering his hand. Loki shook it with overblown dignity, which Tony found hilarious. The Captain didn't so much as twitch, which is why he was their PR go-to guy. He introduced the rest of the Avengers and got Loki's name in return.
"Well, I want to thank you for your help today." The kid beamed again. When Steve settled down and had kids, he'd be a great dad. "And what brings you to Earth?"
"Thor." Loki wrapped his arms around Thor's neck. "The palace has been boring without him, so I've been scrying and watching his adventures." Thor looked worried at that. "And today I saw you were fighting a most mighty foe, so I asked the Queen Mother for permission to come help, and she gave it."
"You were a big help today, Loki." Cap had his "good job, kiddo" face on. "But in the future, I think you should leave the fighting to adults, okay? Maybe you can join the Avengers when you're older."
"No."
Hah, Tony thought. There's the brat.
"I will be staying with Thor here on Midgard for the foreseeable future."
"Loki--"
"It has already been approved." The kid raised his chin, looking every inch spoiled royalty.
"I will be talking to mother," Thor grumbled. Tony tried not to laugh.
"How are you two related anyway?" Black Widow asked. "Brothers? Cousins?"
Loki puffed up like an offended cat. He locked his ankles around Thor's waist and hugged his arms around his neck even tighter. Tony thought Thor could let him go, and the kid'd just hang there like a limpet.
"I'm not his cousin." Loki gave her a nasty stink-eye. "I'm his wife."