Lord Yellow Dog of the Thirty-One Cuts was a Homeworlder who was one of Larissa's cousins. They came into the world together, and when their family was scattered around the Homeworld due to a madness in their bloodline, they marched together as children to their new home, a small, forgotten house in the mountains.
Instead of sleeping, he liked to go out and explore the house at night, and he told Larissa untrustworthy stories about secret ceremonies, great caverns of machines and ships, and nighttime meetings of wild things with sharp teeth and claws. He also told her of a voice from the deepest, innermost sanctum that was calling his name: not the name Larissa knew him by, but the name he'd have in the dead lands when he didn't exist. The voice agitated him, so he tried to find it; when he came back, he never revealed what he'd seen, and he never spoke of the voice again. He and Larissa grew apart.
Later, he and Larissa were readmitted to their House. When Thessalia recruited Larissa to be her mnemonic, she said she had tried to recruit him to the Order of the Weal but he had been drawn to the interventionists.