So it begins! Welcome to the final arc in Changing of the Guard. What was meant to be an eleven chapter story will end up closer to twenty, but I'm honestly quite happy with what I've written here. I hope you enjoy it! Stick around at the end for some extra details, too!

"Oh God." -Gwen gasps, covering her mouth in shock. "That's a ship."

Sure enough, the largest piece of debris isn't debris at all; it's an enormous warship, orange and black, shaped vaguely like a sideways tuning fork, bulbous crystalline sections on both ends of its 'prongs'. The massive vessel is damaged - indeed, as it clears the uppermost cloud layer, Ben can see barely identifiable fragments of what must've been the Azure Lance lodged into the hull - but it seems to have no problem making its slow descent towards the surface.

To the onlookers, it almost looks like the Earth itself is trying to fight it off, as friction with the air causes small fires to briefly come to life all over the vessel, and static build-up causes thunder and lightning to burst along its path.

"Who's Vilgax? What does he want?" -Coulson demands.

"He's an alien warlord." -Ben explains, deciding the time for any subterfuge has passed. "Old, dangerous - Grandpa Max fought him decades ago, and he was supposed to have killed him, but obviously that's not the case. He's the one who's been sending the huge drones we've been fighting, all because he wants this: the Omnitrix."

Ben holds up the watch, which immediately starts beeping, the faceplate turning in place. The hourglass design shifts into the familiar diamond that showcases his transformations' silhouettes, but this time, instead, it projects a life-sized hologram of Azmuth himself.

"Azmuth?" -Ben wonders, shocked.

"Tennyson." -he greets, curtly. The genius inventor gravely looks up at Vilgax's slowly approaching warship. "I see the Chimeran Hammer has finally caught up to you...and yet, I don't see you searching for off-world transport."

Coulson looks like he's aged about twenty-five years in an instant. "I'm...almost afraid to ask, but...who is this?"

"This is Azmuth, the ancient inventor who created the Omnitrix." -Ben supplies. "He died ages ago, but the watch kept an imprint of him as a sort of sapient AI."

Azmuth scoffs. "There's no time to play catch up with the humans, Ben. Seek transport immediately! Vilgax cannot be allowed to take the Omnitrix from you."

"Sorry sir, the human would like to ask another question." -Coulson says, sarcastically. "As a representative of mankind's foremost defense authority, I need to know what kind of threat this Vilgax character poses."

"Oh, you'll be fine, I'm sure. If Vilgax is at all the man he used to be, he'll leave Earth alone as long as the Omnitrix isn't here." -he waves him off, impatiently, narrowing his oversized eyes at Ben. "Which would be easier if we were on our way off-world, Ben."

"Sounds good to me. We don't have any interstellar vessels, but S.W.O.R.D. definitely does." -Coulson muses. "I guess it's time to stop ignoring Director Brand's calls."

Ben shakes his head. "Now, hold on, guys." -he says. "I didn't agree to any of this. In fact, I'm not going anywhere. Vilgax wants the Omnitrix, he can try and take it."

The adults protest, Azmuth loudest of all. "You most certainly are not. It's true that you've grown remarkably proficient with the Omnitrix in a very short time span, but even Max wasn't Vilgax's equal at his prime - it took him, a full Nova fleet, and the entirety of the Plumbers joining forces to defeat him. All that, and it wasn't even permanent, as you can plainly see."

"More importantly, this isn't a game, Mr. Tennyson." -Coulson chastises. "I admire your commitment, but staying here will only put innocent lives at risk. I can't allow it."

"You say these things like I haven't considered them already. Leaving now will only lead to Vilgax following along and spreading destruction in his wake. We have to stop him, here and now, with the home field advantage. We've managed just fine against his giant drones and hired guns on our own - if we all join forces, like Grandpa and his team, I know we can beat him." -Ben counters. "I promise you, I don't actually wanna fight him. I don't wanna die at fifteen - there's so much more stuff I wanna do, still." -he admits. "But I gave up that choice when I picked up the Omnitrix, and I couldn't live with myself if I didn't at least try."

Azmuth shakes his head, heavily. "Your bravado betrays how little you actually know about what's at stake here, Ben. If you succumb to Vilgax, you won't just be endangering this small settlement, or even a few planets - you'll doom this entire galaxy. I won't allow my creation to be used for war. I'll take control of it, if I must." -he threatens.

Ben scowls. "You'll prove Tetrax right if you do. He believed you were a liar, and a hypocrite." -he argues. "You can't say you believe in me, and tell me the Omnitrix is mine to command, and then threaten to take control of my body away because I'm not doing what you want. As long as I breathe and this watch is on my wrist, I'll use its power to protect people - and right now, that means facing down Vilgax."

The Galvan scientist wavers. "This is a mistake, Benjamin." -he warns.

"If it is, it's my mistake." -Ben says, resolute. "Please. Let me prove myself worthy of the Omnitrix."

Azmuth sighs, pausing for a moment. "...much to my chagrin, it should be quite obvious you already are." -he admits. "This course of action may be idiotic, but...it's also quite admirable. Were this a different situation, I couldn't be prouder of my creation's bearer. As the odds are stacked against you, however...well, all I can give you is my blessing - and thus the best possible chance for your success." -he says.

"Omnitrix: Activate Master Control." -Azmuth intones. If anyone expected some kind of fanfare, they'd be disappointed, as the watch merely pulses twice in confirmation. The ancient Galvan begins to dematerialize, the ghost of a smile on his amphibian lips. "Good luck, Ben."

Ben's eyes widen. "What did he just do?" -Julie wonders.

"I...I think he just gave Ben the keys to the kingdom." -Kevin says, in awe.

It's not a feature of the watch they've ever discussed, but Ben knows this; he saw some of his alternate adult selves using it during the interdimensional showcase inside the Omnitrix, but even if he hadn't, he'd still know, the same way he knew how to activate the watch for the first time, despite never having seen it in his life. To test his hypothesis, he thinks back to that first moment - of the thrill of plunging into a hitherto unknown world of powerful aliens, ancient inventors, and a life of heroism unlike any other.

In a flash of neon green, Heatblast stands before them. Barely a moment passes, and another flash turns him to Diamondhead. Just to prove a point, Goop follows, and then the others. Ripjaws. Big Chill. XLR8. Upgrade. Four Arms. And finally, the ones he hasn't had a chance to fight with yet, Overflow and Echo-Echo. Back in human form, his mouth splits in a wide grin. "Oh, now it's hero time."

"It's anything but." -Coulson says. "You may have convinced the small alien, but that's not gonna work with me. You're going to stand down, and we'll get you as far away from a populated area as possible, for S.W.O.R.D. to pick you up and take you away from Earth."

"Yeah, I'm gonna take a pass on that." -Ben says, sarcastic.

Coulson scowls. "Please, Ben. Don't make me arrest you."

In a flash of emerald light, Heatblast looms over the balding man. "Hate to tell you this, Agent Coulson, but your chances of taking me in were just reduced to zero. Now, you and the rest of S.H.I.E.L.D. can help us protect Arcadia...or you can get out of our town, and out of our way."

As if on cue, Vilgax's ship finally reaches its intended destination, hovering some twenty thousand feet in the air, ten or so miles away from the outskirts of town. It's hard to tell at this distance, at first, but it promptly beings disgorging a sizeable complement of dropships and drones, flying towards Arcadia at a leisurely pace.

"I'm going to take out as many of those troops as I can. You guys protect the citizens for me." -Heatblast tells the group. He turns to Coulson. "Can I trust you to evacuate the town?"

Coulson wavers, seeing the teenagers so determined to do their part. He sighs, after a moment. "Azmuth was right. This is a bad idea." -he laments. "We'll do what we can, Ben, but my team here wasn't sent for a fight."

Heatblast nods. "Understood."

"If you're really gonna do this...don't be a hero. Play it safe, delay their forces as much as possible without overextending yourself - no doubt the Avengers are already on their way, but the trip from New York will still take over two hours." -he advises. "I'll need any information you can give me on the enemy we're facing, too."

"I can help with that." -Kevin pipes up. "You guys still have my Plumber's Badge, or have you already tried to dismantle it?"

"You can have your gear back." -Coulson reassures him. "There a way for us to communicate with you, Ben?"

Heatblast points at their flaming corona. "Probably shouldn't risk any heat-sensitive equipment on me."

"I'll come with." -Gwen suggests. "Give me an earpiece, and I'll relay anything relevant between you two."

Coulson agrees, handing her a spare he apparently keeps in his suit pocket. "It's decided, then. Good luck, everybody."

The agent walks away towards the command center, Kevin following along after sparing a worried glance for the cousins. "So...this is it, huh?" -Julie mutters.

Heatblast winks at her. "We'll be fine, Jules." -they reassure her. "Like I said...I have a lot left I wanna do, and a lot of that's with you."

Julie manages a shaky smile. "I'll hold you to that, Ben." -she says. "Just...please be careful, alright? I love you."

It's not the first time either of them have said it, but it does feel much more significant now, minutes away from what's sure to be the fight of their lives. "I love you too, Jules. Stay safe."

With that, Julie runs off, following the others. Heatblast closes their eyes and takes a moment to center themselves, breathing deeply. "You ready for this?" -Heatblast asks.

"Ready as I'll ever be." -Gwen says, donning the earpiece. "Can you imagine, going back and telling your obnoxious little ten year-old self you'd be saving the world someday?"

Heatblast winces. "Oh, God, I don't even wanna imagine myself getting the Omnitrix so young. Think my head would get so big it'd spontaneously explode."

"Don't I know it." -Gwen retorts, amused. Her eyes take on that trademark violet glow, and she nods, mostly to herself. "Alright, then. Let's do this."

The Pyronite responds by pooling fire between his palms, and blasting the soil under him, as if to form a makeshift thruster. It's a tricky technique, to be sure - one they can't imagine any but the most daring Pyronites would even attempt - and even with their Omnitrix-given instincts, it's taken quite a bit of practice to master. Before long, though, they're rocketing through the air, and towards the alien warship, Gwen taking flight not far behind.

A quick evaluation of the aerial battlefield ahead is...dire. There's at least a hundred hovering drones the size of minivans making their way towards Arcadia, and below them, a contingent of man-sized insectoid robots, easily a thousand strong, deposited by dropships now returning to the mothership. Two dozen or so of the giant drones they've been facing march right among the soldiers - and that means something close to fifty of their shoulder mounted support drones just waiting to be sprung as reinforcements.

Somewhere in the back of their mind, the RTS player in Ben has to compliment Vilgax for bringing in some well diversified forces.

As soon as they're in range, the aerial drones open fire, sizzling bolts of red energy zipping by Heatblast and Gwen. The blasts are powerful, but sporadic, which leaves them a good enough window to dodge and form deflective shields, respectively. Heatblast lands on the first drone they reach, using it as a platform to bathe the closest drones in searing plasma, instantly frying their inner electronics and reducing much of their armored plating to molten slag. Their makeshift platform doesn't last long, shot by friendly fire and beginning to melt from Heatblast's presence alone, so they jump to the closest one, and begin the process anew.

Meanwhile, Gwen forms a disc of sorts above her head, channeling her energy through it and blasting at the troops below. Each sweep of the beam incinerates a swath of drones, but she finds herself having to devote most of her focus to dodging and protecting herself from the hail of laser blasts they fire in retaliation, so she ascends further, joining Ben in the aerial fray.

Coulson finds himself grimly ignoring traffic law and flooring it, as he receives the initial report on the enemy's forces from Miss Tennyson.

He's leading S.H.I.E.L.D.'s small contingent to the highway heading east out of Arcadia, a more or less deserted plain from which Vilgax's troops will be attacking. They're setting up a number of barricades along the way - a line they'll attempt to hold for as long as possible. Hill stayed behind, coordinating efforts between S.H.I.E.L.D. and the country's armed forces to repel the invasion, President Ellis having given the green light for a full response. ETA on their support is decent, if worrying, considering no one was prepared for a second invasion so soon after the Chitauri - the first Raptor squad will be on the scene in a little over twenty minutes, and it'll take the National Guard closer to an hour to arrive. As predicted, the Avengers are on track to arrive in two whole hours, though he imagines Tony will arrive much faster, owing to his usual impatience and the suit's incredible top speeds. S.H.I.E.L.D. itself won't be able to send troops until tomorrow, since their mobile base is on dry dock for repairs and most of their ground forces are deployed around the world, and S.W.O.R.D., from what little Director Brand was willing to say, is frantically searching for survivors among the wreckage of the allied Kree fleet.

At the rate the enemy is coming, Coulson thinks they're gonna have to break King Leonidas' record and pull off a modern remix of the Battle of Thermopylae.

"Your arm is broken, isn't it?" -Kevin drawls, lightly punching her metal shoulder as he directs a throng of confused locals towards the hidden S.H.I.E.L.D. camp they've established as a relatively safe space to wait out the invasion.

Julie scowls. It's been harder and harder to hide, but Kevin's right; the fight with SixSix damaged much of the inner mechanisms of her prosthetic, to the point that she's considering taking it off to avoid the occasional stabbing pains to her stump caused by the fried sensors and misfiring servomotors. "I guess I overdid it with SixSix." -she admits. "Not like we can fix it, now that the Kree are gone."

"They're a hardy people, Julie. I'm sure most of them made it." -he tries to reassure her.

"You saw what's left of the Lance." -Julie retorts. "There's no way Hala survived. And if she didn't survive, there's no reason for the others to help us, which means I'm stuck with this."

Kevin shrugs. "I'll give it a go as soon as we get a breather, promise. I'm no Kree engineer, but this puppy can figure any machine out." -he says, holding up the Plumber's badge. "Pretty confident I can at least get it to stop hurting you."

Julie scoffs. "You're assuming we actually get a moment to rest. Hearing Gwen's report, I think we'll be lucky to survive."

"Way I see it, you won't have to worry about your arm if we die. Win-win." -he jokes.

She laughs, against her own will. "You're terrible at pep talks, you know that?"

"And you're terrible at being peppy." -he retorts. Kevin puts a comforting hand on her shoulder - the flesh and blood one, this time. "We'll make it, Julie. I trust Ben to see this through, and I trust us to help him out."

Julie mutely nods. It's a nice moment amidst the tension, further broken by the car honk version of La Cucaracha approaching them. Stuart pulls up to the curb, looking equal parts terrified and excited. There's a small creature on his shoulder - kind of like a baby version of Ben's Upgrade form, which is just...bizarre to think about. "Fine day for an alien invasion, eh fellas?" -Stuart chuckles, nervously.

"Guess it could've happened on a Monday." -Julie says, sarcastic. "Who's your little friend?"

The mini-Mechamorph perks up. "Ship-ship-ship!" -it says, pointing a blob-like appendage towards Vilgax's warship looming in the distance.

"It's an Extrusion - something like a drone produced by Galvanic Mechamorphs when they wanna multitask." -Kevin explains. "It's got a pretty limited AI, but it can upgrade tech just as well as...well, Upgrade."

"Benji lent it to me so I could escape the coppers earlier today. Long story, not that it's worth telling it now, living through history in the making as we are." -Stuart says. "Thought the little chap would vanish on me after it fulfilled its purpose, like a regular Extrusion, but I suppose the Omnitrix is powerful enough to keep him around indefinitely."

Julie hums. "You say it can upgrade stuff, but can it repair things, too?" -she wonders, holding up her malfunctioning prosthetic.

The Extrusion leans toward the offered arm, almost as if it were a dog sniffing curiously at a new toy. "Ship, ship!" -it chirps, gleeful.

"Looks to me like it can." -Kevin says. "Why does it only say 'ship', though?"

"Kinda reminds me of a Pokémon. Maybe that could be its name?" -Julie smirks. "Hey, um...you mind if I borrow Ship?" -she asks Stuart.

"Oh, come now, you named it! Honestly Julie, just keep it, will you? I already have something of a handful in Buster as a pet." -he reassures her. "Oughta give your arm quite the extra kick."

The newly minted Ship becomes fluid, then, and merges with the Kree prosthetic. Almost immediately, the pain and discomfort ceases, and her arm not only feels repaired, but so life-like that she honestly can't tell the difference between it and her normal limb, aside from the obviously metallic look and texture to the black and green prosthetic. She flexes her fingers in wonder at the borderline magical technology on display, her eyes welling with tears as she feels the cooling afternoon air caress her fingertips.

"Wow." -she whispers. Ship's little face protrudes from her palm, expectantly. "Thank you, Ship."

It's a quiet, beautiful moment - which makes her mother screaming in horror at seeing the alien clinging to her daughter all the more notorious.

Fifteen minutes of non-stop fighting later, it feels like they've barely made a dent.

It's not like their efforts have been fruitless, at least; they've managed to dramatically reduce the number of flying drones the defenders back at Arcadia have to contend with, since they're mostly destroyed or busy trying to kill them. Still, Vilgax's ship seems to produce an endless supply of them, and they've barely managed to devote any firepower to the ground troops, which means Arcadia still faces an actual army.

Big Chill dives through a flying drone, freezing its internals solid and causing it to plummet. They then transform into Echo-Echo, who multiplies into half a dozen copies, all of them jumping onto separate drones and screaming them to pieces. Merging back together, they reform into Goop, and subsequently explode into a shower of acidic goo that eats through metal and plastic alike before pulling back into a cohesive mass and transforming into Heatblast to gain back the lost altitude and start over.

Gwen, for her part, is barely recognizable; unleashing so much of her power has burned away the skin of her arms, revealing the Anodite within, the same thing happening to her eyes and feet. She doesn't even know if she can even grow so much of it back, but there's no point in dwelling on it - she'd rather look like the alien she truly is than hold anything back and let her beloved hometown be destroyed. It's utter chaos, but they've so far managed to stay on top of it.

So far.

It almost happens too quickly for Gwen to see it; Ben, as Heatblast, strays a little too close to Vilgax's warship in his haste to pursue a squad of flying drones, and apparently, comes in range of the dreadnought's point-defense systems. A powerful laser bolt shoots out of a swivelling turret, perfectly tracking Ben.

She reaches out, desperate to protect her cousin, but Ben manages to shock her by becoming Diamondhead at the last possible moment; the bolt still strikes him, sending him plummeting down to Earth, but at least he's in one piece. Gwen dives towards him, wincing as he hits the ground hard, making a sizable crater amidst the marching troops. The insectoid robots once again pepper her with blaster bolts, but she manages to put up a stronger shield this time, blasting back at them with her own magenta beams and forcing them to pull back a bit.

Gwen lands beside her cousin, who's groaning as he takes a moment to compose himself. She projects a dome around them, as strong as she dares to make it. "You alright?" -she breathes heavily.

"Yeah. Almost wasn't." -he admits, turning back to Ben and rising to his feet. "Kinda wishing that Master Control had also unlocked the whole alien database. I wouldn't mind turning into some of the bigger aliens I saw my fellow Omnitrix wielders become."

The redhead rolls her eyes. "And here I thought you were happy to have a number of aliens that rhymed with your name. What happened to 'Ben 10's just good for branding, Gwen', huh, dweeb?"

"Vilgax and his alien army happened." -he says, deadpan. He nods at her steadily receding humanity. "How're you doing?"

She shrugs. "Just fine. It doesn't hurt, I'm just...really regretting buying that expensive bikini, now." -she laments.

Ben snorts. "I'm sure your boyfriend won't mind either way."

"Ugh. Let's just survive this battle so I can berate you for linking my desire to look good with my feelings for Kevin, alright?"

A flash of emerald, and Heatblast points at her. "A-HA! So you do have feelings for Kevin!"

"Jesus Christ. I love you, Ben, but I kinda really, really hate you sometimes."

"Gotta keep our spirits up somehow." -they smirk. "Ready for round 2?"

"No." -she admits. "But let's do it anyway."

Gwen drops the shield, and flies away, drawing the attention of more flyers. Heatblast, on the other hand, stays put. The troops fire at them, chipping tiny bits of rock of their form. It doesn't hurt, and whatever mineral their body is made of seems to repair itself, but it is rather annoying.

"You really wanna see what I can do? Fine. I'll show ya, punks." -they grind out.

Fists clenching as they pool their power, their fiery aura flares outward, becoming a maelstrom of flame around them that renders the blaster bolts streaking toward them completely ineffectual. The sandstone beneath their feet bubbles, molten, glassed by the sheer amounts of heat, and with a savage roar, they let the inferno loose.

To Gwen, it looks like a solar flare has erupted on Earth - jets of plasma spraying every which way and igniting the very air into a pyre of white flames that incinerate everything around them - quite literally atomizing the closest few ranks of soldier drones. The ones farther away melt down to varying degrees - some rendered down to glowing slag, others managing to escape the blaze relatively functional. She must be a mile away, and she still has to shield herself from the heatwave, lest her human skin be fully burned away.

It's a wonder to behold - the power of the Omnitrix unbound by a species' normal biological limitations or the watch's own timer system. She can see why Azmuth was so reluctant to allow Ben its full use, and why he seemed so terrified of Vilgax taking it for his own; in the wrong hands, the Omnitrix could be a weapon capable of decimating armies, perhaps even entire worlds.

Her wonder doesn't last long - swiftly turning to horror, as the warship shudders open. Large panels on its top slide ajar, revealing a massive figure - only vaguely humanoid in shape, green and orange in color - flesh, metal, and circuitry turning what must've originally been some kind of cephalopod-like lifeform into an upright, towering giant, lit crimson by the inner glow of his ship.

"I am Vilgax." -he proclaims, his voice equal parts hissing, gargling, and booming, somehow heard over the noise of an entire battlefield. "And the Omnitrix is mine."

I have a somewhat embarrassing confession to make: even though I have about ten Google Docs pages of background information I use for reference in this fic, I somehow managed to make Ben's playlist 9 aliens, instead of the ideal 10. I could've sworn I had that ready, but reviewing this chapter - and the scene with Ben switching between his transformations at will - I realized I only had 9 names, even accounting for the missing Echo-Echo. So, I picked one from the pool of future unlocks in Overflow, a transformation from the Reboot series. I know it's a very unpopular interpretation of Ben 10 - I think it's fine, for what it's intended to be, if you're gonna hate on it, please don't do it in my comments - but it does have some fun designs, and I personally prefer Overflow to Water Hazard, the two fulfilling near-identical power niches. Here are the final (?) codex entries:

Echo-Echo:
The Omnitrix's sample of a Sonorosian, from the planet Sonorosia. Echo-Echo is a being composed of pure, living soundwaves, contained within a specialized silicon suit. He can detect the slightest of vibrations, and can emit modulated sounds of up to 175 decibels, louder than the loudest sound ever recorded on Earth. He can also generate copies of himself, the better to create a "wall of sound" to attack with. Echo-Echo is also very agile, but his body is relatively fragile, which makes his copies easy to destroy. As a tidbit, he also struggles to speak normally, because his species usually communicates at volumes akin to that of a jet turbine.

Overflow:
The Omnitrix's sample of a Cascan, from the planet Cascareau. Overflow is a creature composed of a never-ending sentient water source, encased in a suit of robotic armor. Overflow produces water jets from his wrists that can be strong enough to punch through steel. He can manipulate large volumes of water, and absorb them into his body. Overflow is extremely vulnerable to electric attacks, and his robotic shell can be disabled or even destroyed. Were this to happen, the Omnitrix would generate another, though he would be an immobile puddle of water in the meantime.

That leads me to talk about Master Control! I've talked about it when asked in reviews and comments before, but I won't be taking it away from Ben at the end of this. It's annoying even when it serves a purpose in the animated shows in keeping the status quo more or less intact, and I don't have to bow to such limitations, so it's here to stay. The catch is that Ben can only swap back and forth between his unlocked aliens, not the whole dang library, or even an expanded one, and of course, he can still make the wrong call and be defeated for it. The training wheels are off, so to speak.

Finally, let's talk Vilgax. I rewatched most of his original series appearances (that's by and large the incarnation he's derived from) and while I'm absolutely keeping his overall aesthetic and some of his demeanor, my version will be a lot colder, more calculating, but also easier to empathize with in his motivations and goals. The hammy portrayal works very well for the original series, but not so much here.. I'll spell out why after next chapter, but suffice it to say, this Vilgax has had a rough go of it. Still, there'll be more than a few remixed nods to his original appearance, and in terms of powers and abilities he'll be very similar.

That's about it, for now! I had a lot of fun playing around with Ben's usage of Master Control, even though I normally don't enjoy fight scenes. Also devoted entirely too much time to making some rough calculations in order to write a single paragraph of Coulson figuring out when support will arrive, but that was super fun, too. And finally reuniting Julie and Ship! Anyway, I hope you enjoyed the chapter!

As always, thank you for your attention! Make sure to comment or message me if you have any questions about this story. Look me up on Twitter as Darthkvzn or Tumblr as darthkvznblogs if you'd like - and on Ko-fi, as Darthkvzn, if you like what I do and have a buck to spare.

Until next time!