As it was in Spire Lyn, the stone walls of the cavern were bone white, and the dusty floor was red rust. Stalagmites and stalactites filled the space like the teeth of some predatory beast. In some places, the cavern was dark and filled with a blue haze, while in other places it resembled a narrow canyon, the open sky framed by a foliage canopy, with sun shafts illuminating the rusty gravel. Creaky wooden staircases allowed passage through the steeper descents, and ferns grew in the places where the light touched. Occasionally entire walls would open up to the sky, revealing the great pines which grew just beyond the escarpment. Some chambers were devoid of sunlight, illuminated only by a strange bioluminescent fungus which hung from the cavern ceiling, like a night sky painted with teal stars.


    The five students marched ahead with Vince in the lead, trailed by a pair of burly Aden family soldiers. Kiera and Claire lingered behind, along with a pair of handmaids and the Eyes of Flame, the royal oculomancer. It was the first time that Kiera had ever seen the caverns before, though this was not the case for Claire. They both wore thick wool dresses and sturdy boots, and they were both armed with tall hiking axes, a weapon which made Kiera feel somewhat uncomfortable to hold.


    The group came upon an underground chasm. The sconces on the near and far walls illuminated the bone-white rock, but the chasm was of such a depth that the light could not penetrate the darkness below. An arched ethersteel bridge, glowing with a slight cyan light, spanned the chasm at an angle. The bridge looked brand new, completely devoid of imperfections, and this put Kiera''s mind at ease as they crossed the chasm.


    Just beyond the chasm, the tunnel split in two directions. To the south-east, the path continued upward in a gentle slope, open to the air on one side. The south-western fork ended in an imposing stone gate, draped to either side with the red banner of House Aden. Two guards waited for them at the fork. They both wore red robes and shining ebony masks that obscured their faces, and unlike the Aden soldiers, they were both armed with spirit-lattice ethersteel swords, not unlike the spear carried by Sir Zachary.


    "My princess," one of the guards said with a deep bow. "Why have you come? Why have you brought these commoners with you?"


    Claire Aden marched forward and said, "We are just going to see some birds on the plateau to the south."


    The guard waved his black-gloved hand to the east, pointing to the ascending path, and said, "Move along then. Move along."


    Vince took the lead and marched off along the eastern path, an act which provoked the others to follow. Soon the caverns opened up into switchbacks upon the side of a mountain, leading up and to the west. The sky above was clear and blue, as the mountain rose far above the thin layer of misty fog. Spire Lyn dominated the sky to the south, braced in stacked rings of greenhouses. Half a dozen airships were ferrying workers between the base of the spire and the greenhouses, and a seventh airship was slowly ascending toward the bowl-shaped city at the apex.


    "I did not know that airships could fly all the way to the top," Quinn said. "Though I suppose it makes sense. How else are the witches going to get up there? Princess Kiera, have you been to the top of a spire before?"


    "Yes! I rode an airship to the top, just like that one," Kiera lied. "It took a very long time. They are quite slow."


    "I wonder if you could fly an airship to the Sister World?" Quinn asked.


    "That would take too long," Kiera insisted. "You would run out of food and starve to death."


    "That''s probably true," Quinn admitted.


    The final switchback aligned the path with the spine of the mountain, winding up and up to meet with a bone-white escarpment. When the group crested the escarpment, they entered into another world. Tiny, sparse blades of grass grew from the rusty soil in a few places between the white rocks. Below, the stone dropped away into an eroded plateau, where a few pools of blue-turquoise water rested at different levels, surrounded by wave-like copses of pines. The shady places were crusted with a thin layer of snow. The peaks at the opposite end of the plateau were all very dark gray and jagged and coated with a dusty layer of pale rubble.


    "It''s beautiful!" Kiera said.


    "I''ve been here before," Claire said. "Me and Lucia went swimming in one of these lakes in summer."


    "Sounds like a good way to freeze to death."


    "Lucia used ethermancy to heat the water. It was actually quite comfortable."


    "Was she naked?" Kiera whispered.


    "I was ready for her foolishness," Claire replied proudly. "I brought her bathing suit too."If you discover this tale on Amazon, be aware that it has been stolen. Please report the violation.


    There was a ledge directly to the south. To the west, the ledge overlooked a steep descent into some copses surrounding an alpine lake. The eastern escarpment overlooked a forested valley, thousands of feet straight down. Vince led them to the west, carefully negotiating the rocky switchbacks with practiced confidence. The spike at the end of Kiera''s hiking axe turned out to be very handy for keeping balance on the snow-crusted rocks in the shadowy places. She was happy that Claire forced her to bring the weapon.


    Before they had even reached the lake, the determined silence of the group was shattered by the piercing cry of an eagle. The creature circled high above the lake, its great wings outstretched and unmoving in a gentle glide. Even from the ground Kiera could see that the wings ended in long finger-like feathers.


    Wanting to make conversation, Kiera asked, "Mister Vince. What is the significance of the feathers at the very end of the eagle''s wings?"


    "Excellent question!" He beamed. "Ornithologists have studied the topic of wing shape extensively, and I have repeated some of their observations in the field."


    He paused for a few moments in silence.


    "Princess, you must forgive me. Please allow me to point out some other wing shapes first, and I promise I will return to the topic of the eagle''s wings when that is done."


    "A lovely idea," Kiera said.


    When they reached the copse, the ground leveled off toward the shore and the treacherous rocks were replaced with even more treacherous roots. Finally they came upon the shore of the alpine lake, where the water was glowing like an opal in the sunlight. Small, fat birds rested on the rocks to the south, and in the middle of the lake a pair of black swans lazily preened themselves.


    "Hey look!" Claire said. "That''s my family sigil!"


    "That''s right," Vince said. "That''s Aden''s Swan. It is a migratory bird. In the winter they can be found on the peninsula far to the west of where I live."


    The man set down his tripod, and from his pack he produced a spyglass with a comically large lens, which he secured to the top of the tripod. He peered through the device for a few moments, and then beckoned Quinn to approach.


    "On the far side of the lake," Vince said. "Hurry! There is one gliding just above the water."


    After Quinn peered through the spyglass, he was shoved aside by the golden whelp Irene. Then Kiera bullied her way to the strange device and peered through as well. The device at the neck of the tripod was crafted such that the spyglass could be manipulated with some resistance. Through the dark-framed bauble of her vision, she caught a glimpse of the creature as it was skimming the water to land. Unlike the eagle, this bird had pointed wings.


    "We call them high-speed wings. They can be found on ducks and falcons as well. The ornithologists say that the rapid wingbeats are very energy intensive, and the birds require a great deal of food to survive. Their diet might inspire them to migrate in the winter."


    Next, he turned the spyglass to face the fat birds resting on the rocks. Their feathers were the same color and texture as the rock, and they had tiny feathers in the nostrils at the top of their beaks.


    "These are a type of local quail," Vince explained. "Their wings are very short and prominently slotted. Unlike the swans, they stay put in the winter, and they molt their feathers and grow new ones that blend in with the snow. They do not fly in the winter, and even in the summer they only really fly short distances to escape predators. However, when in flight they are highly maneuverable, which helps them navigate dense vegetation."


    "So the finger-like feathers aid in maneuverability?" Quinn asked.


    "They are called slotted wings, and that is correct. They aid in both maneuvering and takeoff."


    "I don''t think we will be able to add those slotted wings to the kite," Seth said. "The mechanisms would be too complicated. I can''t imagine how I would control them."


    "Perhaps it would be like learning to ride a bike?" Quinn offered.


    "I don''t think so," Bjorn said. "The mathematics required to control those features are instinctual to the birds. No human pilot would be able to learn the technique."


    "When I am at sea," Irene said, "I sometimes witness birds floating just above the waves. They have wings that are very long and straight, and a perfectly straight tail. How do you call this creature?"


    "That may be an albatross," Vince said. "Here, I might have a sketch."


    He rifled through his folio of painted sketches and offered one to Irene. The bird looked like a large seagull, with wings that together formed an arch worthy to support a bridge. The very tips of the wings were perfectly straight, without the finger-like feathers.


    "The albatross can soar over the ocean for very long periods of time. In fact, the ornithologists theorize that they might be able to circle our world without stopping. They are very efficient ocean foragers. However, their weakness is that they struggle to leave the ground in the first place. Their wings are designed for soaring, and they are very inefficient during takeoff."


    "So there is a tradeoff between flight and takeoff," Quinn said. "Fascinating. I''ll bet we can use this. Brother, would it be possible to change the shape of the wing specifically for takeoff?"


    "I will add that to the list of problems to solve," Seth said. "After we figure out how to stop the kite from diving nose-first into the ground."


    "So what about the eagle?" Kiera asked.


    "Ah yes! The eagle is a compromise between the albatross and the quail. Their wings allow for soaring, as we see directly above us, but they are much shorter than the wings of an albatross. The slotted wings aid in takeoff."


    "The mystery is solved," Claire said. "But I''m hungry! Mister Vince, are those quail birds tasty?"


    "I cannot say," Vince admitted. "I would kindly ask..."


    But it was too late. Claire Aden tapped one of the soldiers on the elbow, and without hesitation, and with perfect swiftness, he aimed down his rifle''s sight and pulled the trigger. The sound of gunfire echoed across the alpine lakes, scaring away the swans and the surviving quail.


    "Excellent shot!" the Eyes of Flame said.


    The second soldier tapped his pack with a metallic clank. "We''ll go start a fire and cook him up for you, princess. I warn you quail is an acquired taste."


    That day Kiera discovered that quail was, indeed, an acquired taste.