We still have time," Kell assured him, getting to his feet."How do you know?" asked Hastra. "We can't hear the bells down here, and there are no windows to gauge the light." "Magic," Kell said, and then, when Hastra's eyes widened, he gestured to the hourglass sitting on the table with his other tools. "And that.
V.E. Schwab, A Gathering of Shadows
a-gathering-of-shadows, hastra, humor, kell, magic