Comfortable with his leadership role as head of the Brockton Bay Wards, the PRT intended to test this leadership by having him swap with Weld from Boston. Recognized as capable and intelligent by the criminal elements in the city. Like all teenagers he had something to prove which would come back to bite him.
Carlos is described as a young man of Puerto Rican descent who wore his hair long. He wears a rust-red costume with a matching helmet, both with silver-white trim, and a shield emblem. During his first appearance, however, he switched costumes with Clockblocker as part of a plan to trick the Undersiders.
Aegis possesses the ability of flight and an augmented physiology that operates at peak capacity as long as he is still living.His entire biology is filled with so many redundancies and reinforcements that it makes it very difficult to put him down. For example: blinding him allows him to see by sensing light through his skin, cutting his throat bleeds no more than cutting the back of his hand, cutting off an arm would only last until he could get it reattached and stabbing him in the heart means that other organs would take its place. Aegis could survive decapitation.
During the Wards' confrontation of the Undersiders at the bank, Aegis survived being slammed into the ground hard enough to kill a person, and stood back up after less than a second. Angelica held him in her mouth and whipped him around like a toy, but he kept fighting. After Brutus and Angelica played a game of tug of war with his body, Kid Win hit them with a series of bolts from his Alternator Cannon, blasting the three of them into the opposite building. It took the dogs some time to get up, but Aegis was in the air immediately. 
Aegis' augmented physiology allows him to abuse his body in ways that make him appear to possess supernatural strength. He can throw punches hard enough that they’d break his hand, mangle his joints and tear his muscles, and his body will take it. He can further enhance his strength by undergoing adrenaline rushes that he can keep going for hours. This has the further side effect of making it so that he never gets tired. He was able to deliver a two-handed blow to Brutus' snout that knocked him over onto his side.
In addition to his flight and augmented physiology, Aegis does not seem to feel pain, although his powers allow him to deal with the drawbacks. It is left unclear if Aegis truly possessed a congenital insensitivity to pain (CIP) or if he simply had an incredible ability to simply "deal" with the sensation. Strictly speaking with his adaptive brute ability Aegis would be able to defeat Glory Girl.
During the battle at the Bank, Aegis led the Brockton Bay Wards to the bank after it was learned that the Undersiders were robbing it. He switched costumes with Clockblocker in an attempt to fool the Undersiders and have Clockblocker tag them - an attempt to remove the majority of the Undersiders' fire power in one fell swoop. He then lined up with the other Wards across from the bank and waited for the Undersiders to attempt to make a break for it.
Following the Undersiders' release of some of their hostages, Grue flooded the street with darkness. Hellhound and her dogs emerged from the darkness and headed towards Clockblocker, but thanks to Tattletale's forewarning, they switched course and go after Aegis instead of Clockblocker. He held his ground against Brutus and Angelica, but ended up receiving severe damage to his borrowed costume. Kid Win rescued him by blasting both Aegis and the dogs with his Alternator Cannon.
He emerged from the rubble and flew into the air to get a bird's eye view to try and find the villains, but Grue filled every street and side street with his darkness as he escaped.
Panacea asked who needed the most help, but Aegis told her that he would live and volunteered to be the last person healed. Gallant spoke up and Panacea followed him to a private space to get healed while Aegis stayed behind. He later looked up as Panacea emerged, picked up a marker and began to write down information in the column that had been made for Tattletale. He was healed later.
Aegis later appeared alongside New Wave's fliers following the reveal of the Empire Eighty-Eight's identities and Purity's subsequent rampage. Crusader and Rune ran interference for Purity, distracting and trapping the heroes so that Purity could blast them out of the sky.
Director Piggot eventually decided to restructure the Brockton Bay Protectorate and Wards team and planned to swap Aegis with Weld. She and the PRT wanted to see how Aegis would handle leading a different team.
However, before the Director could implement her plan, Brockton Bay suffered an Endbringer attack. Aegis was seen talking among the Brockton Bay Wards near New Wave. He then listened as Legend gave a pre-battle speech.
Aegis helped distribute armbands to the gathered heroes and villains that would help coordinate them in the upcoming fight before joining the group of front-line combatants led by Alexandria and Dragon. He, along with the rest of the group, were teleported out of the base by Strider upon Leviathan's arrival.
Later in the battle, when Leviathan was heaving himself out of a building's remains and used his tail to fling debris at the assembled capes, Aegis threw himself at the incoming projectiles. Despite his efforts, two capes were struck down while a third was cut in half by the water from Leviathan's tail.
When Leviathan was trapped, Aegis was assigned to an aerial route to prevent it from heading to the rooftops. He was killed when the Endbringer escaped. His body was so completely and utterly smashed that his powers couldn't do a thing to prevent his death. The damage was so absolute that no redundancy in his system could keep the resulting pulp alive.
Brian shook his head, “Lisa, want to field this one?”
She did. “Aegis isn’t strong, but he can abuse his body in ways that makes it seem like he is. He can throw punches hard enough that they’d break his hand, mangle his joints and tear his muscles, and his body just takes it. He has no reason to hold back, and he doesn’t need to waste any time protecting himself from you. He can also draw on adrenaline… you’ve heard stories like how little old grandmothers lifted cars off the ground to save their grandkids?”
“That’s adrenaline at work, and Aegis can do that for hours at a stretch. His body doesn’t run out of steam, he doesn’t get tired, he doesn’t exhaust his reserves of adrenaline. He just keeps going.”
“So how do you stop him?” I asked.
“You don’t, really,” Brian said, “Best bet is to keep him occupied, keep him sufficiently distracted or stick him somewhere he can’t escape. Trap him in a dumpster and throw it in the river, you can get a few minutes of relief. Which is all harder than it sounds. He’s the team captain, and he isn’t stupid." - Excerpt from Agitation 3.3
↑Aegis probably lived (sheer dumb luck and the fact that he had something to prove in defending his home city that killed him in the first place), as did Gallant (who didn't go to Florida). - Excerpt from speculation by Wildbow on Reddit
↑Carlos returned from the shower, wearing sweatpants and a towel around his shoulders. He was Puerto Rican, his hair long. His body was clean of blood, barring a few residual trickles from the mess of ragged wounds on his arms, stomach and chest. He had clumsily stitched the cuts and gouges together, which did surprisingly little to make them easier to look at. He sat down on a chair and added his input for the lists, which didn’t amount to too much. He had been incapacitated for too much of the fight to have much to say. - Excerpt from Interlude 3
↑Aegis – A young hero with a rust red and silver costume, with a shield emblem. Leads the Wards in his first appearance, has a biology filled with redundancies and safeguards, rendering him able to function no matter how damaged he is. - Cast (spoiler free)
↑Carlos Aegis Redundant biology, operating at peak capacity so long as alive, possessed of flight and ability to use body with no fear of self harm. Wards Brute Mover - Parahuman List; bolded edit by Wildbow
↑Aegis (Deceased) – Powers included flight and an augmented physiology that lacks any weak points. Onetime team leader of the local Wards team. Wore a rust and silver costume with a shield emblem. Perished in the Endbringer arc. - Cast Page (In-Depth)
↑ 8.08.18.2“Sure,” he said, “So let’s go down the list. Team leader: Aegis. You’d think he has the standard Alexandria package, flight, super strength, invincibility, but that isn’t exactly right. He does fly, but the other two powers work differently than you’d expect. See, he isn’t invincible… he just doesn’t have any weak points. His entire biology is filled with so many redundancies and reinforcements that you just can’t put him down. Throw sand in his eyes and he can still see by sensing the light on his skin. Cut his throat and it doesn’t bleed any more than the back of his hand would. The guy’s had an arm cut off and it was attached and working fine the next day. Stab him through the heart and another organ takes over the necessary functions.”
“Not that we’re stabbing anyone through the heart?” I made it a hopeful half-question, half-statement.
“No. Well, it wouldn’t be a bad idea to stab Aegis through the heart just to slow him down. If you did it with something big enough. The guy’s like a zombie, he gets back up within seconds of you beating him down, keeps coming at you until you’re too tired to fight back or you make a mistake.” - Excerpt from Agitation 3.3
↑ 9.09.19.2Aegis bolted the second the dog changed course, but it was too late. As he tried to fly out of reach, Judas leaped, nearly twice as far and high as I might have guessed something as big as he was could. The dog’s prehensile tail wrapped around Aegis’ torso. As they all fell, mount, rider and ensnared captive, Bitch shouted something I couldn’t hear, and Judas whipped Aegis straight down, adding the force of the throw to the momentum of the fall.
I thought I might have heard the impact from the interior of the bank. Or maybe it was as auditory illusion and my bugs were the ones who heard it. Either way, Aegis hit the ground hard enough to kill an ordinary person.
He wasn’t down for one second before he was on his feet again. In the same motion he used to get to his feet, he lunged for the dog and swung a fist at Judas’ snout.
Strong enough to slam a two ton dog to the side with one blow, chomped on by said dogs, whipped around like a chew toy, and continues to fight without slowing down. - Excerpt from Agitation 3.9
↑ 10.010.1He swiveled the cannon to face Judas, who was still guarding the spot where Bitch had fallen. A bolt of light erupted from the cannon and sent Judas flying beyond my field of vision. He fired another shot, at a greater distance, presumably at the fallen dog. Then he swiveled and fired off two more shots in quick succession, blasting Aegis and the two dogs that were gripping him.
The dogs and Aegis were all sent flying into the wall of the office building opposite the bank. While the dogs didn’t get up immediately, a bloody and tattered Aegis was on his feet in an instant, and in the air a moment later. He got to a good height – maybe two or three stories up, and stayed there, likely to get his bearings and survey the situation. - Excerpt from Agitation 3.10
↑While I’d been distracted by Clockblocker, Bitch had set Brutus and Angelica on Aegis. He was fending the two dogs off, but the white pane of his helm – Clockblocker’s helm – was shattered, now, and his costume was torn with one piece of ruined armor dangling by a string of cloth at his armpit.
Brutus lunged for Aegis, but as he passed over the edge of the area Vista had distorted, he fell short. The dog’s jaws clacked shut a foot away from Aegis’ face, spittle flying.
Aegis responded by slamming both fists, fingers interlaced, into Brutus’ snout. The dog crashed onto its side, giving Aegis the time to take flight once more, heading straight for the sky.
If I was surprised to see that display of acrobatics from one of the dogs, I doubted there were words for what Aegis’ must have felt, just then. Angelica seized the teen hero in her jaws and they plummeted together.
Angelica didn’t land with all four claws beneath her, and she sprawled as she hit the ground. When she stopped, though, she still had Aegis, one of his arms and half his torso clasped between her teeth. She whipped him around like a dog might shake a toy. When she paused, he was still fighting her, slamming his free hand against the side of her head over and over. Loops and strings of drool mixed with blood hung from her mouth. At least, that’s what I thought it was, from my vantage point inside the bank, peering through gloom and pouring rain. - Excerpt from Agitation 3.9
↑ 12.012.1AceOfSword: With his redundant biology he could have survived getting bissected I'm pretty sure. Aegis doesn't have any special protection against damage but most of the wounds he get turn out to be minor to him. Getting beheaded would probably only slow him down. It was pure bad luck that Aegis, who could have survived a lot of damage, got crushed into paste: even his redundant biology couldn't keep him alive when all of his body got wrecked.
Wildbow: Brutes (esp. regenerators) and changers often relocate their cores/coronas to the hardest to access part of their body, or adapt to do without. Crawler's wasn't in his brain, for example.
↑We got on the dogs, and Regent fired a salvo of shots from the laser cannon into Aegis, hammering him into the side of a building until the wall around him collapsed - Excerpt from Agitation 3.12
↑The problems with CIP (Congenital Insensitivity to Pain) don't tend to afflict someone with a natural ability to simply deal. Infection? Psh. Scratched corneas? He can see if his eyes get plucked out. Broken bones? Sections of muscle simply go rigid and offer the structure. - Reddit comment by Wildbow
↑“Director Piggot. Ma’am,” Aegis greeted her, his voice strained. His costume was in shreds, and was more crimson with his own blood than it was its original white. It was bad enough his civilian identity might have been revealed, if it weren’t for the matted blood and the chunks of meat that had been taken out of him, some of the wounds nearly a foot across.
“Good god, Aegis,” her eyebrows raised a fraction, “You look like hell. What’s wrong with your voice?”
“Punctured lung, ma’am,” Aegis rasped, “I think there’s a hole in my front and back.” As if to demonstrate, he stuck his fingers into his chest cavity.
Director Piggot didn’t look away, but one of the men standing behind her looked a touch green around the gills, “I can take you at your word. You don’t need to stick your arm all the way through your chest to demonstrate.” - Excerpt from Interlude 3
↑“Piggot has decided to take action in reflection of recent events. Both the Wards and the Protectorate are being restructured.”
Hannah winced, “How bad?”
Shrugging, Colin told her, “As far as the Wards go, we’re losing Aegis. Piggot and the PRT want to see how he does leading a different team, and the boy’s parents are amenable. He’ll stay in the Wards for a little longer, to suggest he’s younger than he is.”
↑Manpower deceased, CD-6. Aegis deceased, CD-6, my armband spoke, at the same moment my bugs reached the area around where Leviathan had been.
He was awake again.
Aegis would have been covering an aerial route, keeping Leviathan from heading to the rooftops, which meant Leviathan went up. I had the mass of roaches ascend, trying to get a sense of his location. I tried to use my armband to help gauge the direction he was traveling, but since I couldn’t move my arm, it was difficult at best. - Excerpt from Extermination 8.4
↑“It was bad. She took Glory Girl with her, you know. When Gallant died, Vista saw the body. When Aegis was mashed to a literal pulp by Leviathan, to the point that he couldn’t function anymore, when he died, despite his power? I got to see the remains to verify for myself. But Victoria Dallon was still alive and they didn’t let us see. A select few adults and family members got to see her, they carted her off to a parahuman asylum and none of the rest of us got to say goodbye, because the end result was that fucked up.” - Excerpt from Queen 18.3
↑I spent a long time writing in this universe, and pretty much every character that shows up (or 95% of them) featured in the various snippets I wrote - I was struggling to write and rarely got past five pages, but it did a lot to help me wrap my head around the world and how it all fit together.