But it still wasn't enough.

"Hold your lines!" Katie Gardner shouted, somewhere off to my left.

The problem was there were too few of us to hold anything. The entrance to Olympus was twenty feet behind me. A ring of brave demigods, Hunters, and nature spirits guarded the doors. I slashed and hacked, destroying everything m my path, but even I was getting tired, and I couldn't be everywhere at once.

Behind the enemy troops, a few blocks to the east, a bright light began to shine. I thought it was the sunrise. Then I realized Kronos was riding toward us on a golden chariot. A dozen Laistrygonian giants bore torches before him. Two Hyperboreans carried his black-and-purple banners. The Titan lord looked fresh and rested, his powers at full strength. He was taking his time advancing, letting me wear myself down.

Annabeth appeared next to me. "We have to fall back to the doorway. Hold it at all costs!"

She was right. I was about to order a retreat when I heard the hunting horn.

It cut through the noise of the battle like a fire alarm. A chorus of horns answered from all around us, echoing off the buildings of Manhattan.

I glanced at Thalia, but she just frowned.

"Not the Hunters," she assured me. "We're all here."

"Then who?"

The horns got louder. I couldn't tell where they were coming from because of the echo, but it sounded like an entire army was approaching.

I was afraid it might be more enemies, but Kronos's forces looked as confused as we were. Giants lowered their clubs. Dracaenae hissed. Even Kronos's honor guard looked uneasy.

Then, to our left, a hundred monsters cried out at once. Kronos's entire northern flank surged forward. I thought we were doomed, but they didn't attack. They ran straight past us and crashed into their southern allies.

A new blast of horns shattered the night. The air shimmered. In a blur of movement, an entire cavalry appeared as if dropping out of light speed.

"Yeah, baby!" a voice wailed. "PARTY!"

A shower of arrows arced over our heads and slammed into the enemy, vaporizing hundreds of demons. But these weren't regular arrows. They made whizzy sounds as they flew, like WHEEEEEE! Some had pinwheels attached to them. Others had boxing gloves rather than points.

"Centaurs!" Annabeth yelled.

The Party Pony army exploded into our midst in a riot of colors: tie-dyed shirts, rainbow Afro wigs, oversize sunglasses, and war-painted faces. Some had slogans scrawled across their flanks like HORSEZ PWN or KRONOS SUX.

Hundreds of them filled the entire block. My brain couldn't process everything I saw, but I knew if I were the enemy, I'd be running.

"Percy!" Chiron shouted across the sea of wild centaurs. He was dressed in armor from the waist up, his bow in his hand, and he was grinning in satisfaction. "Sorry we're late!"

"DUDE!" Another centaur yelled. "Talk later. WASTE MONSTERS NOW!"

He locked and loaded a double-barrel paint gun and blasted an enemy hellhound bright pink. The paint must've been mixed with Celestial bronze dust or something, because as soon as it splattered the hellhound, the monster yelped and dissolved into a pink-and-black puddle.

"PARTY PONIES.'" a centaur yelled. "SOUTH FLORIDA!"

Somewhere across the battlefield, a twangy voice yelled back, "HEART OF TEXAS CHAPTER!"

"HAWAII OWNS YOUR FACES!" a third one shouted.

It was the most beautiful thing I'd ever seen. The entire Titan army turned and fled, pushed back by a flood of paintballs, arrows, swords, and NERF baseball bats. The centaurs trampled everything in their path.

"Stop running, you fools!" Kronos yelled. "Stand and ACKK!"

That last part was because a panicked Hyperborean giant stumbled backward and sat on top of him. The lord of time disappeared under a giant blue butt.

We pushed them for several blocks until Chiron yelled, "HOLD! On your promise, HOLD!"

It wasn't easy, but eventually the order got relayed up and down the ranks of centaurs, and they started to pull back, letting the enemy flee.

"Chiron's smart," Annabeth said, wiping the sweat off her face. "If we pursue, we'll get too spread out. We need to regroup."

"But the enemy—"

"They're not defeated," she agreed. "But the dawn is coming. At least we've bought some time."

I didn't like pulling back, but I knew she was right. I watched as the last of the telkhines scuttled toward the East River. Then reluctantly I turned and headed back toward the Empire State Building.

We set up a two-block perimeter, with a command tent at the Empire State Building. Chiron informed us that the Party Ponies had sent chapters from almost every state in the Union: forty from California, two from Rhode Island, thirty from Illinois . . . Roughly five hundred total had answered his call, but even with that many, we couldn't defend more than a few blocks.

"Dude," said a centaur named Larry. His T-shirt identified him as BIG CHIEF UBER GUY, NEW MEXICO CHAPTER. "That was more fun than our last convention in Vegas!"

"Yeah," said Owen from South Dakota. He wore a black leather jacket and an old WWII army helmet. "We totally wasted them!"

Chiron patted Owen on the back. "You did well, my friends, but don't get careless. Kronos should never be underestimated. Now why don't you visit the diner on West 33rd and get some breakfast? I hear the Delaware chapter found a stash of root beer."

"Root beer!" They almost trampled each other as they galloped off.

Chiron smiled. Annabeth gave him a big hug, and Mrs. O'Leary licked his face.

"Ack," he grumbled. "Enough of that, dog. Yes, I'm glad to see you too."

"Chiron, thanks," I said. "Talk about saving the day."

He shrugged. "I'm sorry it took so long. Centaurs travel fast, as you know. We can bend distance as we ride. Even so, getting all the centaurs together was no easy task. The Party Ponies are not exactly organized."

"How'd you get through the magic defenses around the city?" Annabeth asked.

"They slowed us down a bit," Chiron admitted, "but I think they're intended mostly to keep mortals out. Kronos doesn't want puny humans getting in the way of his great victory."

"So maybe other reinforcements can get through," I said hopefully.

Chiron stroked his beard. "Perhaps, though time is short. As soon as Kronos regroups, he will attack again. Without the element of surprise on our side . . ."

I understood what he meant. Kronos wasn't beaten. Not by a long shot. I half hoped Kronos had been squashed under that Hyperborean giant's butt, but I knew better. He'd be back, tonight at the latest.

"And Typhon?" I asked.

Chiron's face darkened. "The gods are tiring. Dionysus was incapacitated yesterday. Typhon smashed his chariot, and the wine god went down somewhere m the Appalachians. No one has seen him since. Hephaestus is out of action as well. He was thrown from the battle so hard he created a new lake in West Virginia. He will heal, but not soon enough to help. The others still fight. They've managed to slow Typhon's approach. But the monster can not be stopped. He will arrive in New York by this time tomorrow. Once he and Kronos combine forces—"

"Then what chance do we have?" I said. "We can't hold out another day."

"We'll have to," Thalia said. "I'll see about setting some new traps around the perimeter."

She looked exhausted. Her jacket was smeared in grime and monster dust, but she managed to get to her feet and stagger off.

"I will help her," Chiron decided. "I should make sure my brethren don't go too overboard with the root beer."

I thought "too overboard" pretty much summed up the Party Ponies, but Chiron cantered off, leaving Annabeth and me alone.

She cleaned the monster slime off her knife. I'd seen her do that hundreds of times, but I'd never thought about why she cared so much about the blade.