The courtyard of Boreas Keep smelled like a dead dragon.
The "Black Blood"—twenty barrels of it hauled from the mines—sat in the center of the bailey, giving off a stench of sulfur and rot that made the horses nervous.
"It stinks, My Lord," Lena said, wrinkling her nose. She was holding a cloth over her face. "And it smokes when we burn it. The refugees in the Great Hall are coughing. If we use this for lamps, we'll suffocate before spring."
"Crude oil is a cocktail, Lena," I said, walking around the barrels. "It's a mix of heavy chains and light chains. Right now, we're burning the dirt along with the spirit."
I turned to Tessa. She was covered in soot, looking more comfortable than she had in the palace silk.
"Tessa, I need a column," I ordered. "Iron. Tall. Hollow. And I need copper plates inside it, spaced every six inches."
"A pipe?" she asked.
"A tower," I corrected. "A Distillation Column."
We spent the day building it. It was a ten-foot-tall iron cylinder standing vertically over a brick furnace. Inside, I had instructed Tessa to weld a series of perforated copper trays.
"The Physics," I explained to my confused audience (Giles, Hareth, and Elara), drawing a diagram in the dirt.
"Oil is a mixture of liquids with different boiling points. When we boil the black sludge at the bottom, it turns into vapor. The vapor rises up the tower."
I pointed to the top of the tower drawing.
"As the vapor goes up, it cools down. The heavy stuff—the thick oil—condenses back into liquid on the bottom trays. The lighter stuff—the lamp spirit—keeps rising to the top before it turns back into liquid."
I looked at them.
"It's a sorting machine. Gravity sorts the heavy. Heat sorts the light."
We fired the furnace. I poured the first bucket of black sludge into the boiler at the base.
We waited. The iron groaned as it heated up.
"Tessa," I said. "Monitor the pressure. If the rivets start to hiss, pull the fire."
"It's humming," she whispered, her hand hovering near the metal. "The liquid inside... it's dancing."
Half an hour later, the taps I had installed at different heights began to drip.
From the bottom tap: A thick, black goo. Thicker than the crude.
"Tar," I said, catching it in a bucket. "Asphalt. Hareth, remember the cracks in the outer wall? The water freezes in the cracks and breaks the stone?"
"Aye, My Lord."
"This is the cure. We boil this tar and pour it into the cracks. It seals the stone. It stops the water. It waterproofs the roof."
From the middle tap: A brownish, oily liquid.
"Lubricant," I noted. "For the wagon axles. No more rancid grease."
And then, from the very top tap, a clear, thin liquid began to trickle out. It smelled sharp, chemical, and clean.
I caught it in a glass jar. It looked like water, but it shimmered.
"Kerosene," I whispered.
"What is it?" Elara asked, peering at the clear liquid.
"The Spirit of the Rock," I said. "Giles, bring me a wick."
I dipped a piece of cotton into the kerosene. I set it on a saucer and lit it.
It didn't flare with dirty orange smoke like the crude oil. It burned with a steady, brilliant, white flame. No smoke. No smell. Just pure, high-efficiency lumens.
"By the Gods," Hareth breathed. "It's brighter than a wax candle."
"It's refined energy," I said, capping the jar. "With this, we can light the Keep all night without choking. With this, we can signal across the valley."
I looked at the black tar bucket and the clear kerosene jar.
"We turn the waste into walls," I said. "And we turn the spirit into light."
Suddenly, a horn blew from the battlements. It was a jagged, frantic sound.
"Sentry!" Hareth barked, spinning around.
A guard on the wall was pointing toward the treeline.
"Movement!" the guard screamed. "At the edge of the jungle! Something big!"
I grabbed my double-paned goggles and ran to the wall. Elara was right beside me, moving silently despite her bulk.
I strapped the goggles on and looked into the whiteout.
The blizzard was thinning slightly. Through the swirling snow, I saw shapes. They weren't Yaks.
They were tall—seven feet at least. They wore armor made of bone and ice. Their skin was a pale, necrotized blue. They were carrying heavy iron cleavers.
Frost-Orcs.
And they weren't alone. They were dragging something. A carcass.
One of our Yaks.
"They found the kill site," Hareth cursed, drawing his sword. "They tracked us back."
There were fifty of them. A raiding party. They stood at the base of the causeway, staring up at our gates. They didn't look cold. They looked hungry.
One of them—the leader, wearing a helm made of a polar bear skull—stepped forward. He roared, a sound that shook the snow off the pine trees.
"They are testing us," Elara said, her hand resting on the hilt of her dagger. "They want to see if we will hide."
I looked at the distillation tower bubbling in the courtyard. I looked at the jar of kerosene in my hand. And I looked at the bucket of sticky, boiling tar.
"Hareth," I said calmly. "How do Orcs feel about fire?"
"They hate it, My Lord. But arrows blow out in this wind. We can't hit them with fire."
I looked at Tessa, who had followed us up.
"Tessa," I said. "Can you pressurize a tank?"
"If it is iron, yes."
"Good."
I turned to Hareth. "Captain. Bring the tar buckets to the wall. And bring the pump from the water wagon."
"My Lord?"
I smiled, and for the first time, the black teeth looked less like a corpse and more like a predator.
"We aren't going to shoot arrows at them," I said. "We are going to introduce them to the concept of Napalm."
"Elara," I handed her the jar of kerosene. "You're the igniter. When I spray the tar... you provide the spark."
The Engineering Phase was over. The Defense Phase had begun.