Mathias Thais is a Lodestar in the Cancrian Royal Guard who becomes Rho's Guide when the stars choose her to be the new Holy Mother.
When Rho enrolled in the Cancrian Academy on Elara, the largest moon in the Crab constellation, she was a lonely twelve-year-old who missed her family and longed to be back on her beloved Blue Planet. While wandering the Academy compound one morning, which they shared with the adjoining Zodai University, she stumbled upon a large solarium. Inside was an older, beautiful boy with dark hair and indigo blue eyes; he was going through the motions of Yarrot.
Rho was immediately drawn to his beauty and quiet poise, and she returned to the solarium early every morning, before anyone else was up, seeking the serenity she felt in his presence. The sense of home.
Since she was so much younger than him, Mathias never noticed Rho--until now. When the stars reunite them at the Lunar Quadract celebration on Elara, Rho is on the cusp of seventeen, awaiting her admissions decision from Zodai University, where Mathias attended.
He graduated first in his class and was the youngest Lodestar to be recruited into the Zodai Royal Guard in a century. Now that Rho is named Cancer's new leader, she asks Mathias to be her Guide. Though torn between his heart and his mind, Mathias accepts.
Along with Hysan Dax, they venture through the galaxy to warn the other Houses about Ophichus although he still doesn't believes much in it..