Ok, here's a detailed background. If Daria doesn't work out as his mentor, I can modify it to a different mentor.
Josserand was born in a small village in the Vosges Mountains, where his parents were simple shepherds. Even then, there was something strange with young Josserand. Like his mother, he had pure white hair even as a child, which marked him as different from the dark-haired folks of the village. He began running almost as soon as he could stand, darting here and there chasing the sheep or the chicken. He liked to feel the wind on his face, he would tell his parents when they tried to keep him still. He was also quick to anger, much to the despair of his mother, who saw her own father's anger reflected in the child.
While he was still a young child, Josserand's parents died of a fever that struck the village. He was taken in and raised by his uncle Enguerrand, a woodcutter working in the mountainous forests of the Vosges. This was a lonely and hard life, one which Enguerrand had until then lived alone, for no woman wanted to live in the woods. But Enguerrand had a strong sense of duty, and the boy had no other close family, so he took charge of his brother's son. This period was hard on both of them, as Enguerrand was ill-equiped to raise this quick-tempered child, while Josserand missed his mother desperately. Still, they both had little choice in the matter, if for different reasons.
One day, while Enguerrand was in the village with Josserand, he was approached by a man to act as a guide for his small party. They were seeking a certain valley, he said, for their mistress who had heard of its holy properties. Not one to spit upon some hard coins, which were hard to come by in a small village, Enguerrand accepted. Little did he know that the man worked for a maga of the Order, Clara Stella of Tremere, who was seeking a magical spring in the mountains. She had noticed that unusual winds seemed to blow around the boy, who also displayed other signs of the Gift. So she had arranged to hire Enguerrand as a guide in the mountains in order to observe the boy more closely. This proved satisfactory to her. Upon their return to the village, she had her man negociate with the uncle to take charge of Josserand. Enguerrand hesitated, for there was something strange with all of that business of apprenticing Josserand to a stranger. But for some reason, he accepted, not knowing that he was being manipulated by the maga's magic into accepting.
While she didn't intend to take him as her own apprentice, Clara knew that her House would find a use for the boy and train him. So she brought him home and had him tutored in Latin before passing him on to a more senior Tremere for evaluation. The boy's aptitudes were tested for weeks. It was found out that he carried the legacy of a minor Roman god of old, Aquilon the northern wind that brings winter. He had the latent ability to move like the winds and an affinity with the winds. This particular mythic heritage had not been encountered before by House Tremere, but it was decided that it might be well-suited for the role of scout. So he was apprenticed to a Tremere of the Lineage of Muj (HoH:MC p.77), Teodor Tremeris, who was instructed to preserve the boy's particular talents intact rather than shape him into the usual magus of this lineage. The House wanted to evaluate whether this particular type of Mythic Blood could be harnessed into a different type of scouts. As a result, Josserand was not taught the usual ways of the lineage, but allowed to develop his own innate talents. Still, much of his training emphasized esprit de corps, inculcating a deep loyalty and sense of obligation towards House Tremere. Clara kept in touch with the boy, through letters and the occasional visit, fostering a privileged relationship with him and acting as a mentor.
Late during his apprenticeship, the House had Josserand father a number of children. There is hope that some of these might inherit his Mythic Blood, so that if the experiment proves a success, a new lineage might be fostered. House Tremere plans for the long term.
After passing his Gauntlet, Josserand was given the name Animus by his pater. He was then assigned to Germania, under the reponsibility of Stentorius of Fengheld, who currently holds his sigil as Exarch of the Tribunal.