Meanwhile, at the base of the tunnel, flashes of lightning pinpointed the location of the legion’s standard. Tendrils of electricity zigzagged down the hillsides, arcing through enemy lines and frying them to dust. Camp Jupiter’s ballistae launched giant flaming spears at the invaders, raking through their lines and starting more forest fires. The emperors’ troops kept coming.

The ones making the best progress were huddled behind large armored vehicles that crawled on eight legs and…Oh, gods. My guts felt like they’d gotten tangled in my bike chain. Those weren’t vehicles.

“Myrmekes,” I said. “Meg, those are myr—”

“I see them.” She didn’t even slow down. “It doesn’t change anything. Come on!”

How could it not change anything? We’d faced a nest of those giant ants at Camp Half-Blood and barely survived. Meg had nearly been pulped into Gerber’s larvae purée.

Now we were confronting myrmekes trained for war, snapping trees in half with their pincers and spraying acid to melt through the camp’s defensive pickets.

This was a brand-new flavor of horrible.

“We’ll never get through their lines!” I protested.

“Lavinia’s secret tunnel.”

“It collapsed!”

“Not that tunnel. A different secret tunnel.”

“How many does she have?”

“Dunno. A lot? C’mon.”

With that rousing oratory complete, Meg pedaled onward. I followed, having nothing better to do.

She led me up a dead-end street to a generator station at the base of an electrical tower. The area was ringed in barbed-wire fencing, but the gate stood wide open. If Meg had told me to climb the tower, I would have given up and made my peace with zombie eternity. Instead, she pointed to the side of the generator, where metal doors were set into the concrete like the entrance to a storm cellar or a bomb shelter.

“Hold my bike,” she said.

She jumped off and summoned one of her swords. With a single strike, she slashed through the padlocked chains, then pulled open the doors, revealing a dark shaft slanting downward at a precarious angle.

“Perfect,” she said. “It’s big enough to ride through.”

“What?”

She hopped back on her Go-Glo and plunged into the tunnel, the click, click, click of her bike chain echoing off the concrete walls.

“You have a very broad definition of perfect,” I muttered. Then I coasted in after her.

Much to my surprise, in the total darkness of the tunnel, the Go-Glo bike actually, well, glowed. I suppose I should have expected that. Ahead of me, I could see the faint, fuzzy apparition of Meg’s neon war machine. When I looked down, the yellow aura of my own bike was almost blinding. It did little to help me navigate down the steep shaft, but it would make me a much easier target for enemies to pick out in the gloom. Hooray!

Against all odds, I did not wipe out and break my neck. The tunnel leveled, then began to climb again. I wondered who had excavated this passageway and why they hadn’t installed a convenient lift system so I didn’t have to expend so much energy pedaling.

Somewhere overhead, an explosion shook the tunnel, which was excellent motivation to keep moving. After a bit more sweating and gasping, I realized I could discern a dim square of light ahead of us—an exit covered in branches.

Meg burst straight through it. I wobbled after her, emerging in a landscape lit by fire and lightning and ringing with the sounds of chaos.

We had arrived in the middle of the war zone.

I will give you free advice.

If you plan to pop into a battle, the place you do not want to be is in the middle of it. I recommend the very back, where the general often has a comfortable tent with hors d’oeuvres and beverages.

But the middle? No. Always bad, especially if you arrive on canary-yellow glow-in-the-dark bikes.

As soon as Meg and I emerged, we were spotted by a dozen large humanoids covered in shaggy blond hair. They pointed at us and began to scream.

Khromandae. Wow. I hadn’t seen any of their kind since Dionysus’s drunken invasion of India back in the BCE. Their species has gorgeous gray eyes, but that’s about the only flattering thing I can say about them. Their dirty, shaggy blond pelts make them look like Muppets who have been used as dust rags. Their doglike teeth clearly never get a proper flossing. They are strong, aggressive, and can only communicate in earsplitting shrieks. I once asked Ares and Aphrodite if the Khromandae were their secret love children from their longstanding affair, because they were such a perfect mix of the two Olympians. Ares and Aphrodite did not find that funny.

Meg, like any reasonable child when confronted with a dozen hairy giants, hopped off her bike, summoned her swords, and charged. I yelped in alarm and drew my bow. I was low on arrows after playing catch with the ravens, but I managed to slay six of the Khromandae before Meg reached them. Despite how exhausted she must’ve been, she handily dispatched the remaining six with a blur of her golden blades.

I laughed—actually laughed—with satisfaction. It felt so good to be a decent archer again, and to watch Meg at her swordplay. What a team we made!

That’s one of the dangers of being in a battle. (Along with getting killed.) When things are going well, you tend to get tunnel vision. You zero in on your little area and forget the big picture. As Meg gave the last Khromanda a haircut straight through the chest, I allowed myself to think that we were winning!

Then I scanned our surroundings, and I realized we were surrounded by a whole lot of not winning. Gargantuan ants trampled their way toward us, spewing acid to clear the hillside of skirmishers. Several steaming bodies in Roman armor sprawled in the underbrush, and I did not want to think about who they might have been or how they had died.

Pandai in black Kevlar and helmets, almost invisible in the dusk, glided around on their huge parasail ears, dropping onto any unsuspecting demigod they could find. Higher up, giant eagles fought with giant ravens, their wingtips glinting in the bloodred moonlight. Just a hundred yards to my left, wolf-headed cynocephali howled as they bounded into battle, crashing into the shields of the nearest cohort (the Third?), which looked small and alone and critically undermanned in a sea of bad guys.

That was only on our hill. I could see fires burning across the whole western front along the valley’s borders—maybe half a mile of patchwork battles. Ballistae launched glowing spears from the summits. Catapults hurled boulders that shattered on impact, spraying shards of Imperial gold into the enemy lines. Flaming logs—always a fun Roman party game—rolled down the hillsides, smashing through packs of Earthborn.

For all the legion’s efforts, the enemy kept advancing. On the empty eastbound lanes of Highway 24, the emperors’ main columns marched toward the Caldecott Tunnel, their gold-and-purple banners raised high. Roman colors. Roman emperors bent on destroying the last true Roman legion. This was how it ended, I thought bitterly. Not fighting threats from the outside, but fighting against the ugliest side of our own history.

“TESTUDO!” A centurion’s shout brought my attention back to the Third Cohort. They were struggling to form a protective turtle formation with their shields as the cynocephali swarmed over them in a snarling wave of fur and claws.

“Meg!” I yelled, pointing to the imperiled cohort.