AFTER THAT, THE battle was mayhem.

Hazel, Frank, Percy, and Brooklyn waded through the enemy, plowing down anyone who stood in their way. The First and Second Cohorts fell apart under the assault and the sheer novelty of being on the losing side.

Percy fought like a demon, whirling through the defenders' ranks, slashing with his sword, whacking campers with the flat of his blade, and generally causing mass panic.

And that was why he's Brooklyn's favorite. She grinned maniacally as with one hand, she shot paintballs to startle her enemies, and with her club and her view of the weird red lines, she incapacitated the soldiers.

Octavian screamed in a shrill voice — maybe ordering the First Cohort to stand their ground, maybe trying to sing soprano — which made Brooklyn annoyed, so she made him stop. She used a lightning bolt to separate a line of defenders and swung her club at him, an electric shock shocking him before knocking him out.

"That'll teach you," she smirked.

Frank shot arrows until his quiver was empty, using blunt-tipped missiles that wouldn't kill but left some nasty bruises. He broke his pilum over a defender's head, then drew a sword and started using that.

Meanwhile, Hazel climbed onto Hannibal's back. She charged toward the center of the fort, grinning down at her friends. "Let's go, slowpokes!"

They ran to the center of the base. The inner keep was virtually unguarded. Obviously the defenders never dreamed an assault would get this far. Hannibal busted down the huge doors. Inside,  a few people were sitting around a table playing Mythomagic with cards and figurines. The cohort's emblems were propped carelessly against a wall.

Hazel and Hannibal rode straight into the room, and the standard-bearers fell backward out of their chairs. Hannibal stepped on the table, and game pieces scattered.

By the time the rest of the cohort caught up with them, Brooklyn, Percy, and Frank had disarmed the enemies, grabbed the banners, and climbed onto Hannibal's back with Hazel. They marched out of the keep triumphantly with the enemy colors.

The Fifth Cohort formed ranks around them. Together they paraded out of the fort, past stunned enemies and lines of equally mystified allies.

Reyna circled low overhead on her pegasus. "The game is won!" She sounded as if she were trying not to laugh. "Assemble for honors!"

Slowly the campers regrouped on the Field of Mars. Brooklyn saw plenty of minor injuries—some burns, broken bones, black eyes, cuts and gashes, plus a lot of very interesting hairdos from fires and exploding water cannons — but nothing that couldn't be fixed.

Percy turned toward Brooklyn on the elephant and gave her a grin, taking her hand and shaking it. "Not bad, Hayward," he said.

"You weren't that bad yourself," she told him, part of her brain telling her that he was right there. Like, duh, obviously, but he was really close to her.

She could've stared at his eyes for a long time, but then she heard it.

"Help!" somebody yelled. A couple of campers rushed out of the fortress, carrying a girl on a stretcher. They set her down, and other kids started running over. From the top of the elephant, Brooklyn could tell it was Gwen. She was in bad shape. She lay on her side on the stretcher with a pilum sticking out of her armor — almost like she was holding it between her chest and her arm, but there was too much blood.

Percy slid off of the elephant. Brooklyn hopped off, miraculously landing on her feet with only a small amount of pain and they ran into the crowd.

The medics barked at everyone to stand back and give her air. The whole legion fell silent as the healers worked — trying to get gauze and powdered unicorn horn under Gwen's armor to stop the bleeding, trying to force some nectar into her mouth. Gwen didn't move. Her face was ashen gray.

Finally one of the medics looked up at Reyna and shook his head.

For a moment, there was no sound except water from the ruined cannons trickling down the walls of the fort. Hannibal nuzzled Gwen's hair with his trunk.

Reyna surveyed the campers from her pegasus. Her expression was as hard and dark as iron. "There will be an investigation. Whoever did this, you cost the legion a good officer. Honorable death is one thing, but this . . ."

And then Gwen gasped.

Everyone stepped back. She opened her eyes. The color came back to her face.

"Wh-what is it?" she blinked. "What's everyone staring at?" she didn't seem to notice the seven-foot harpoon sticking out through her chest.

Near Brooklyn, a medic whispered, "There's no way. She was dead. She has to be dead."

Gwen tried to sit up, but couldn't. "There was a river, and a man asking . . . for a coin? I turned around and the exit door was open. So I just . . . I just left. I don't understand. What's happened?"

Everyone stared at her in horror. Nobody tried to help.

"Gwen." Frank knelt next to her. "Don't try to get up. Just close your eyes for a second, okay?"

"Why? What—"

"Just trust me."

Gwen did what he asked.

Frank grabbed the shaft of the pilum below its tip, but his hands were shaky. "Percy, Brooks, Hazel — help me."

One of the medics realized what he was planning. "Don't!" he said. "You might—"

"What?" Hazel snapped. "Make it worse?"

Frank took a deep breath. "Hold her steady. One, two, three!"

He pulled the pilum out from the front. Gwen didn't even wince. The blood stopped quickly.

Hazel bent down to examine the wound. "It's closing on its own," she said. "I don't know how, but—"

"I feel fine," Gwen protested. "What's everyone worried about?"

With Frank and Percy's help, she got to her feet.

"Gwen," Hazel said gently, "there's no easy way to say this. You were dead. Somehow you came back."

"I . . . what?" She stumbled against Frank. Her hand pressed against the ragged hole in her armor. "How — how?"

"Good question." Reyna turned to Nico, who was watching grimly from the edge of the crowd. "Is this some power of Pluto?"

Nico shook his head. "Pluto never lets people return from the dead."

He glanced at Hazel as if warning her to stay quiet. Brooklyn wondered what that was about, but she didn't have time to think about it.

A thunderous voice rolled across the field: Death loses its hold. This is only the beginning.

Campers drew weapons. Hannibal trumpeted nervously. Reyna's pegasus reared, almost throwing her off.

"I know that voice," Percy said. He didn't sound pleased. A small part of Brooklyn's mind also recognized the voice.

In the midst of the legion, a column of fire blasted into the air. Heat seared Brooklyn's eyelashes. Campers who had been soaked by the cannons found their clothes instantly steam-dried. Everyone scrambled backward as a huge soldier stepped out of the explosion.

Her hair stood straight up. The soldier was ten feet tall, dressed in camo. He radiated confidence and power. His black hair was cut in a flat-topped wedge exactly like Frank's. His face was angular and brutal, marked with old knife scars. His eyes were covered with infrared goggles that glowed from inside. He wore a utility belt with a sidearm, a knife holster, and several grenades. In his hands was an oversized M16 rifle.

As most people stepped back, Frank stepped forward. He took three more steps. Then he sank to one knee.

The other campers followed his example and knelt. Even Reyna dismounted.

"That's good," the soldier said. "Kneeling is good. It's been a long time since I've visited Camp Jupiter."

Despite this, Brooklyn wasn't kneeling. Next to her, Percy was glaring at the giant soldier, still hefting his sword.

"You're Ares," Percy said. "What do you want?"

A collective gasp went up from two hundred campers and an elephant. Instead of gasping, Brooklyn just raised her eyebrows, standing her ground.

Instead, the god bared his brilliant white teeth.

"You've got spunk, demigod," he said. "Ares is my Greek form. But to these followers, to the children of Rome, I am Mars — patron of the empire, divine father of Romulus and Remus."

"We've met," Percy said. "We . . . we had a fight . . ."

The god scratched his chin, as if trying to recall. "I fight a lot of people. But I assure you — you've never fought me as Mars. If you had, you'd be dead. Now, kneel, as befits a child of Rome, before you try my patience."

Around Mars's feet, the ground boiled in a circle of flame.

"Percy, Brooks," Frank said, "please."

Brooklyn stared at the god for a moment before eventually kneeling. Percy followed her.

Mars scanned the crowd. "Romans, lend me your ears!" He laughed — a good, hearty bellow, so infectious it almost made Brooklyn smile. "I've always wanted to say that. I come from Olympus with a message. Jupiter doesn't like us communicating directly with mortals, especially nowadays, but he has allowed this exception, as you Romans have always been my special people. I'm only permitted to speak for a few minutes, so listen up."

He pointed at Gwen. "This one should be dead, yet she's not. The monsters you fight no longer return to Tartarus when they are slain. Some mortals who died long ago are now walking the earth again."

Was it Brooklyn's imagination, or did the god glare at Nico di Angelo?

"Thanatos has been chained," Mars announced. "The Doors of Death have been forced open, and no one is policing them — at least, not impartially. Gaea allows our enemies to pour forth into the world of mortals. Her sons the giants are mustering armies against you — armies that you will not be able to kill. Unless Death is unleashed to return to his duties, you will be overrun. You must find Thanatos and free him from the giants. Only he can reverse the tide."

Mars looked around, and noticed that everyone was still silently kneeling. "Oh, you can get up now. Any questions?"

Reyna rose uneasily. She approached the god, followed by Octavian, who was bowing and scraping like a champion groveler.

"Lord Mars," Reyna said, "we are honored."

"Beyond honored," said Octavian. "So far beyond honored—"

"Well?" Mars snapped.

"Well," Reyna said, "Thanatos is the god of death, the lieutenant of Pluto?"

"Right," the god said.

"And you're saying that he's been captured by giants."

"Right."

"And therefore people will stop dying?"

"Not all at once," Mars said. "But the barriers between life and death will continue to weaken. Those who know how to take advantage of this will exploit it. Monsters are already harder to dispatch. Soon they will be completely impossible to kill. Some demigods will also be able to find their way back from the Underworld — like your friend Centurion Shishkebab."

Gwen winced. "Centurion Shish kebab?"

"If left unchecked," Mars continued, "even mortals will eventually find it impossible to die. Can you imagine a world in which no one dies — ever?"

Octavian raised his hand. "But, ah, mighty all-powerful Lord Mars, if we can't die, isn't that a good thing? If we can stay alive indefinitely—"

"Don't be foolish, boy!" Mars bellowed. "Endless slaughter with no conclusion? Carnage without any point? Enemies that rise again and again and can never be killed? Is that what you want?"

"You're the god of war," Percy spoke up. "Don't you want endless carnage?"

Mars's infrared goggles glowed brighter. "Insolent, aren't you? Perhaps I have fought you before. I can understand why I'd want to kill you. I'm the god of Rome, child. I am the god of military might used for a righteous cause. I protect the legions. I am happy to crush my enemies underfoot, but I don't fight without reason. I don't want war without end. You will discover this. You will serve me."

"Not likely," Percy said.

Mars grinned like they were two old buddies talking trash.

"I order a quest!" the god announced. "You will go north and find Thanatos in the land beyond the gods. You will free him and thwart the plans of the giants. Beware Gaea! Beware her son, the eldest giant!"

Hazel made a squeaking sound. "The land beyond the gods?"

Mars stared down at her, his grip tightening on his M16. "That's right, Hazel Levesque. You know what I mean. Everyone here remembers the land where the legion lost its honor! Perhaps if the quest succeeds, and you return by the Feast of Fortuna . . . perhaps then your honor will be restored. If you don't succeed, there won't be any camp left to return to. Rome will be overrun, its legacy lost forever. So my advice is: Don't fail."

Octavian somehow managed to bow even lower. "Um, Lord Mars, just one tiny thing. A quest requires a prophecy, a mystical poem to guide us! We used to get them from the Sibylline books, but now it's up to the augur to glean the will of gods. So if I could just run and get about seventy stuffed animals and possibly a knife—"

"You're the augur?" the god interrupted.

"Y-yes, my lord."

Mars pulled a scroll from his utility belt. "Anyone got a pen?"

The legionnaires stared at him.

Mars sighed. "Two hundred Romans, and no one's got a pen? Never mind!"

He slung his M16 onto his back and pulled out a hand grenade. There were many screaming Romans. Then the grenade morphed into a ballpoint pen, and Mars began to write.

"There!" he finished writing and threw the scroll at Octavian. "A prophecy. You can add it to your books, engrave it on your floor, whatever."

Octavian read the scroll. "This says, 'Go to Alaska. Find Thanatos and free him. Come back by sundown on June twenty-fourth or die.'"

"Yes," Mars said. "Is that not clear?"

"Well, my lord . . . usually prophecies are unclear. They're wrapped in riddles. They rhyme, and . . ."

Mars casually popped another grenade off his belt. "Yes?"

"The prophecy is clear!" Octavian announced. "A quest!"

"Good answer." Mars tapped the grenade to his chin. "Now, what else? There was something else . . . Oh, yes."

He turned to Frank. "C'mere, kid."

He stepped forward.

Mars grinned. "Nice job taking the wall, kid. Who's the ref for this game?"

Reyna raised her hand.

"You see that play, ref?" Mars demanded. "That was my kid. First over the wall, won the game for his team. Unless you're blind, that was an MVP play. You're not blind, are you?"

Reyna looked like she was trying to swallow a mouse. "No, Lord Mars."

"Then make sure he gets the Mural Crown," Mars demanded. "My kid, here!" he yelled at the legion, in case anyone hadn't heard.

"Emily Zhang's son," Mars continued. "She was a good soldier. Good woman. This kid Frank proved his stuff tonight. Happy late birthday, kid. Time you stepped up to a real man's weapon."

He tossed Frank his M16. For a split second Brooklyn thought Frank would be crushed under the weight of the massive assault rifle, but the gun changed in midair, becoming smaller and thinner. When he caught it, the weapon was a spear. It had a shaft of Imperial gold and a strange point like a white bone, flickering with ghostly light.

"The tip is a dragon's tooth," Mars said. "You haven't learned to use your mom's talents yet, have you? Well — that spear will give you some breathing room until you do. You get three charges out of it, so use it wisely."

"Now, my kid Frank Zhang is gonna lead the quest to free Thanatos, unless there are any objections?" Mars asked.

Of course, no one said a word.

"You can take three companions," Mars said. "That's the amount of people needed for this quest. One of them needs to be this kid."

He pointed at Percy. "He's gonna learn some respect for Mars on this trip, or die trying. And you have to go, too," he nodded to Brooklyn. "To prove yourself to our father, and to the rest of our siblings. As for the third, I don't care. Pick whomever you want. Have one of your senate debates. You all are good at those."

The god's image flickered. Lightning crackled across the sky.

"That's my cue," Mars said. "Until next time, Romans. Do not disappoint me!"

The god erupted in flames, and then he was gone.

Reyna turned toward Frank. Her expression was part amazement, part nausea, like she'd finally managed to swallow that mouse. She raised her arm in a Roman salute. "Ave, Frank Zhang, son of Mars."

The whole legion followed her lead, though dread was slowly consuming Brooklyn.

Was this a game? To be forced to go on the quest that would most likely ensure her death?

If it was a game they wanted to play, then it's a game she'll win.