The Heartwood isolation theory

but of course!!

Moments slipped by as they pondered one another, Xerxes regarding Altair with dread curling his belly, fancying that he saw rage and bloodlust flaring into the eyes so like his own. But if a blow was to come, Altair did not cast the first stone, and so the Shah relaxed somewhat, hackles beginning to flatten along the curve of his proud neck. "Ahura alone saw fit to bring us together," Xerxes murmured, the barest hint of chiding in his tone; one did not insult the gods with such insolent claims, though he could not, would not, attempt to reclaim his place as Altair's father. "How did you come to be here?" how long had he been in this place? From where he was, Xerxes had caught no pack-scent upon his wayward son, but that would surely change with time. Or perhaps it would not. "And your mother?" Despite the fact that Nita had won against Zahra, and she had been summarily deposed, and had run away from Samarkand, Xerxes remembered her lovely visage, and the passions that they had shared, that had culminated in the prideful, beautiful son now standing before him now. Perhaps Altair had found her.