She hadn’t been able to find any indication in her reading that people had once known these three notes correlated to the three ancient gods. No Alethi scholars seemed to know that one of these tones could prompt a reaction in Stormlight, though Raboniel had—upon questioning—said she’d known. Indeed, she’d been surprised to learn that Navani had only recently discovered the “pure tones of Roshar,” as she called them.

Navani had tried singing the proper tones, but hadn’t been able to make the light respond. Perhaps she couldn’t match the pitch well enough, because Raboniel had been able to do it—singing and touching one gemstone, then moving her finger to another while holding the note. The Stormlight had followed her finger just as it did a tuning fork.

Today Raboniel was off tending to other tasks, but Navani could use the tuning forks to replicate her singing ability. Three tones: a note for Honor, a note for Odium, and a note for Cultivation. Yet Vorinism only worshipped the Almighty. Honor.

Theology would have to wait for another time. For now, she set up her next experiment. She created streams of Stormlight and Voidlight—drawing each out from a diamond in a corner of her box—and crossed the streams at the center. The two lights pushed upon one another and swirled as they met, but then separated and streamed to their separate forks.

“All right,” Navani said, writing in her notebook. “What about this?” She picked up the partially empty Voidlight diamond and then brought out a fresh Stormlight diamond, fully infused.

In fabrial science, you captured a spren by creating a gemstone with a kind of vacuum in it—you drew out the Stormlight, leaving a sphere with a void or suction inside. It would then pull in a nearby spren, which was made of Light. It was like any pressure differential.

She hoped to be able to refill the Voidlight sphere with Stormlight, now that a portion of the Voidlight had been removed. She hit the tuning fork, started the Stormlight streaming out of its diamond, then tried to get it to go into the Voidlight diamond by making it vibrate to the fork’s tone.

Unfortunately, when she touched the tuning fork to the Voidlight diamond, it immediately stopped vibrating and the tone died. Extinguished like a candle doused with water. She was able to get the Stormlight to bunch up against the Voidlight diamond, by putting the fork next to it, but when she got the Voidlight to stream out toward the side of the table—theoretically creating an active pressure differential in that diamond—she couldn’t get it to suck Stormlight in. Only once all of the Voidlight was out could she infuse the diamond with Stormlight.

“Like oil and water indeed,” she said, making notes. Yet the way the streams didn’t repel one another when touching felt like proof they weren’t opposites.

She rose and—after noting the results of this experiment—went to talk to the Sibling. Navani could easily fool the guards into thinking she was simply strolling among the bookshelves to read a passage or two, as she often did this. Today, she began picking through the books on the back shelf while resting her hand on the Sibling’s vein in the wall.

“Are we being watched?” Navani asked.

I’ve told you, the Sibling said. Voidspren can’t be invisible in the tower. That protection is different from the one suppressing enemy Surgebinders, and Raboniel hasn’t corrupted it yet.

“You also told me you could sense if a Voidspren was near.”

Yes.

“So … are any near?”

No, the Sibling said. You do not trust my word?

“Let’s just call it a healthy paranoia on my part,” Navani said. “Tell me again of—”

You continue to experiment with fabrials, the Sibling interrupted. We need to talk more about that. I do not like what you’ve been doing.

“I haven’t captured any more spren,” Navani whispered. “I’ve been working with Stormlight and Voidlight.”

Dangerous work. The man who forges weapons can claim he’s never killed, but he still prepares for the slaughter.

“If we’re going to restore your abilities, I need to understand how Light works. So unless you have a better idea for me to do this, I’m going to have to continue to use gemstones and—yes—fabrials.”

The Sibling fell silent.

“Tell me again about Towerlight,” Navani said.

This is growing tedious.

“Do you want to be saved, or not?”

… Fine. Towerlight is my Light, the Light I could create.

“Did you need a Bondsmith to make it?”

No. I could make it on my own. And my Bondsmith could create it, through their bond with me.

“And that Light, in turn, powered the tower’s defenses.”

Not only the defenses. Everything.

“Why does it no longer work?”

I already explained that!

“This is a common investigative method,” Navani said calmly, flipping through her book with her left hand. “My goal is to make you restate facts in different ways, leading you to explain things differently—or to remember details you forgot.”

I haven’t forgotten anything. The defenses no longer work because I don’t have the Light for them. I lost most of my strength when I lost the ability to hear the two pure tones of Roshar. I can make only a tiny amount of Light, enough to power a few of the tower’s basic fabrials.

“Two tones of Roshar?” Navani said. “There are three.”

No, there are two. One from my mother, one from my father. The tone of Odium is an interloper. False.

“Could part of the reason you lost your abilities relate to that tone becoming a pure tone of Roshar? Odium truly becoming one of the three gods?”

I … don’t know, the Sibling admitted.

Navani noted this hypothesis.

We need to find a way to restore my Towerlight, the Sibling said, and remove the Voidlight from my system.

“And that,” Navani said, “is exactly what I’m working on.” If she could figure out how to combine two Lights, then it would be the first step toward creating Towerlight.

She clearly needed an emulsifier, a facilitator. What kind of emulsifier could “stick” to Stormlight and make it mix with Voidlight? She shook her head, taking her hand off the vein on the wall. She’d been here too long, so she took a book and strolled to the front of the room, lost in thought. However, as she reached her desk, she found a small box waiting for her.

She glanced at the guard by the door, who nodded. Raboniel had sent it. Navani opened the box, breathless, and found a brightly glowing diamond. At first glance, it seemed to be another Stormlight sphere. But as she held it up and placed it next to a true one, she could see the green tinge to the one Raboniel had sent.

Lifelight. She’d promised to get some for Navani.

“Did she say how she acquired this?” Navani asked.

The guard shook his head.

Navani had a guess. The Sibling had lost sight of Lift, but had explained something was odd about that girl. Something Navani held as a hope that might get them out of this.

Hands steady—though anticipationspren shot up around her—Navani used the middle tuning fork on this new diamond. And it worked: she was able to draw Lifelight out and send it streaming into a gemstone.

Towerlight was Lifelight and Stormlight combined. So perhaps Lifelight—the Light of Cultivation—had some property that allowed it to mix with other Lights. Holding her breath, Navani repeated her earlier experiments, except with Lifelight instead of Voidlight.