I glance over my shoulder. He’s right; I’m safe—if I don’t move again. “Explain what?”

“Do you know why Merlins serve the Legendborn?”

That catches me off guard. “No.”

“Guess.”

His tone is so sharp, I speak slowly to avoid being cut. “To fight the Shadowborn?”

“Adorable.” He rolls his eyes. “The Shadowborn are evil, but don’t think for one second that every Merlin serves the Order wholly out of the goodness of their heart. You called me a crossroads child once, but you don’t fully understand what that means. You can’t.”

He takes another step forward, not enough to push me over but close enough that I can smell lingering spice from the Oath on his skin and feel the warmth rolling off him. A memory of his heated fingers that first night at the Lodge flashes through my mind, and I wonder, just briefly, if the rest of him runs just as hot.

“Merlin children are, for all intents and purposes, fully human at birth. But when we turn seven, the changes begin—the strength, the speed, the senses—and with those changes comes a type of… countdown. Every year after that we gain power and our connection to aether deepens, and every year we lose a bit more of our humanity. We call it ‘succumbing to the blood.’ ” Sel shudders, eyes focusing on me again. “When Merlin created the Legendborn spell for Arthur and his knights, he designed a similar spell for himself. One that would allow all of his descendants to inherit the unique mage abilities he’d honed over time—mesmer, constructs, an affinity for aether.” The tiny tips of his white canines gleam as he speaks. “But Merlin knew his own nature. He knew that demons only care for themselves and chaos, and powerful but uncontrollable part demons would never be compatible servants to the eternal Order he and Arthur envisioned. So, in his spell, Merlin folded in a bit of insurance.”

My chest is suddenly tight. “What kind of insurance?”

Bitterness turns his features sharp in the shadows. “Do you remember when I told you that the hellfox couldn’t dust with a part of you still inside it? That’s because the darkness of the underworld and the light of the living shouldn’t exist in one body. My blood is fighting itself every day. The older I get, the stronger the demon essence becomes, but my commitments to this Order and its members keep me from going over.”

I return his stare, horror and understanding washing over me in a wave. “The Oaths…”