Sebastian is an upside-down Flicker in the fifth-grade Upside-Down Magic class. He is the most mysterious of the UDM class; much about him is unknown, and he has not had a book focused on him, unlike most of the other UDM kids.
Sebastian is a blond boy with thick eyebrows. He dresses formally like, according to Nory, he's going to a tea party.
Sebastian is an upside-down Flicker who sees sound waves. He sees them zip and interact and glow, and often comments on them. The sound waves can be so bright and overwhelming that Sebastian breaks down, unable to function. He begins by using a blindfold, then moves on to an XXL dog cone, and then, in Dragon Overnight, starts using aviatior goggles.
Sebastian is a fussy, earnest boy who has some trouble interacting with others. He likes things neat and proper, and he likes his opinions to be heard. He may come off as a little strange, due to his magic.
Sebastian's backstory is mostly unknown. When she entered the UDM classroom for the first time, Nory thought that his "thuggish" eyebrows meant that he was Pepper, a vicious Fierce.
- Sebastian's magic is impossible to turn off.
- Sebastian conducts the UDM band in the talent show.
- "Sebastian" means "venerable" or "revered".