Joel Castillo is one of IO Fox’s two assistants at Vulpine Dynamics, with Auggie Nakajima. A gray wolf with striking cyan eyes and a long white-and-cyan braid, he is usually in formal clothes or a lab uniform.
He is serious, exacting, and gentle, and people who do not know him find him intimidating. He looks after IO the way family does.
Since September he has lived with the rest of IO’s research team away from the lab (see Chapter 6 - The Return).