Ryuven Binding Oath

Contains spoilers for Books 1-3.

Oniwe’aru stood, and the surrounding Ryuven took a step backward. The humans mimicked them, uncertain of these strange protocols. Oniwe’aru pressed his palms together against his chest and rolled his lower lip into his teeth. Power hummed silently through the air, and then he lifted a hand and pulled his lip free with a little sound of tearing skin.
Ariana flinched.
Oniwe’aru raised his hand and drew a bloody streak across his forehead, left to right. “The Ai will raise no offensive action against Chrenada while we are welcome in your lands, permitted to trade freely and openly. We will suffer no other clan to raise offensive action against Chrenada. We will shepherd our own, keeping our traders safe in strange lands and guarding the honor of our oath. This I swear, the oath of Oniwe, Altayr ni’Ai cin Celæno, Alcyon ni Pairvyn, Majja to Pleione.”

A binding oath is a magically-enhanced pledge, sealing a bit of the Ryuven's own essence into the the promise. Such a pledge cannot be knowingly broken without the oath-speaker suffering real physical and magical consequences, usually debilitating weakness.
Tamaryl made a binding oath to Mage Ewan Hazelrig on the field of Luenda when they first conspired to work together to find an end to the war.