The Iron Trial by Holly Black, Cassandra Clare

nature: Fire wants to burn, water wants to flow, air wants to rise, earth wants to bind, chaos wants to devour.
    3. In all magic, there is an exchange of power.
    4. You can change a thing’s shape, but not its essential nature.
    5. All elements have a counterweight. Fire is the counterweight of water. Air is the counterweight of earth. The counterweight of chaos is the soul.
    “During the tests,” said Master Rufus, “all of you displayed power. But without focus, power is nothing. Fire can either burn down your house or warm it; the difference is in your ability to control the fire. Without focus, working with the elements is very dangerous. I don’t need to tell some of you just how dangerous.”
    Call looked up, expecting to be the one who Master Rufus was staring at, since Master Rufus seemed to always be looking at Call when he said something ominous. This time, however, he was looking at Tamara. Her cheeks flushed and her chin went up defiantly.
    “Four days a week, you three will train with me. On the fifth day, there will be a lecture by one of the other mages, and then, once a month, there will be an exercise in which you will put what you have learned to use. On that day, you may find yourselves either competing against or working with other apprentice groups. Weekends and nights are yours for practice and further study. There is the Library as well as practice rooms, and the Gallery, where you can waste time. Do you have any questions for me before we begin your first lesson?”
    No one spoke. Call wanted to say something about how he’d love some directions to that Gallery place, but he held himself back. He remembered telling his father back at the hangar that he was going to get himself thrown out of the Magisterium, but he’d woken up that morning with the sinking feeling that maybe that wasn’t such a good idea. Trying to flunk the tests in front of Rufus hadn’t worked, after all, so acting out might not either. Master Rufus clearly wasn’t going to let him communicate with Alastair until Call settled in as an apprentice. As much as it galled him to do it, he probably had to be on his best behavior until Rufus relaxed and let him contact his father. Then, when he could finally talk to Alastair, they’d plan his escape.
    He just wished he felt a little more enthusiastic about running away.
    “Very well. Can you guess why I’ve set up the room this way, then?”
    “I’m guessing you need help fortifying your sand castle?” muttered Call under his breath. Even his best behavior apparently wasn’t all that good. Aaron, standing beside him, stifled a laugh.
    Master Rufus raised a single brow but didn’t otherwise acknowledge what Call had said. “I want you three to sit in a circle around the sand. You can sit any way that you’re the most comfortable. Once you’re ready, you must concentrate on moving the sand with your mind. Feel the power in the air around you. Feel the power in the earth. Feel it rise up through the soles of your feet and in the breaths you take. Now focus it. Grain by grain, you are going to separate the sand into two piles — one dark and one light. You may begin!”
    He said it like they were in a race and he’d given them the green light, but Call, Tamara, and Aaron just stared at him in horror. Tamara was the first to find her voice.
    “Separate out the sand?” she said. “But shouldn’t we be learning something more useful? Like fighting rogue elementals or piloting the boat or —”
    “Two piles,” said Rufus. “One light, one dark. Start now.”
    He turned around and walked away. The wall became transparent again as he approached it, then turned back to stone as he passed through.
    “Don’t we even get a tool kit?” Tamara called sadly after him.
    The three of them were alone in a room with no windows and no doors. Call was glad he didn’t have claustrophobia or he’d be chewing off his own arm.
    “Well,” said Aaron, “I guess we should