[1] Septimus is a small and timid-looking boy, with green wizard eyes and curly blond hair, formerly wearing a sheepskin jacket with purple and yellow stripes, and red hat during his Young Army days.

[3] At twelve hours old, Septimus was taken away from his mother Sarah Heap by the Matron Midwife on the commands of the evil Necromancer, DomDaniel.

The third book Physik finds Septimus in great danger as the ghost of an evil Queen Etheldredda sends him back in time 500 years ago.

Events lead to Septimus, Jenna, Beetle and an injured Spit Fyre becoming stranded on a beautiful island and meeting Syrah Syara - a 513-year-old girl possessed by the Syren.

When Jenna, Nicko and he went to find Marcia aboard The Vengeance, he showed his magical skill by being clever enough to utter new spells so that all three of them can see each other even if they are invisible.

When he went back in time to Marcellus Pye, he learnt all that he could about alchemy and "Physik" and was even able to cure the sicknesse which infected the Castle inhabitants.

He is also able to do a complete Projection of a human and keep it relatively solid as he demonstrated in the House of Foryx in Queste, where in the beginning of the book he was able to conjure sound, which many ExtraOrdinary cannot do.

Although he spends most of his time at Wizard Tower, he loves it when he gets a chance to meet Sarah and Silas and roam around the Castle with Jenna as is evident in Flyte.

Septimus loves catching bugs and has vertigo which he faces, many times in the series like when he walks along Snake Slipway in Physik or going along the toll bridge to the House of Foryx in Queste.

It is possible that when he was Boy 412 he had a slight crush on Jenna, as when he would be embarrassed when he had to dress silly in front of her and he would care for her more than any other person, but whether or not he still has it is still unknown.

He does, however, seem to develop a more prominent crush on Syrah Syara, an ExtraOrdinary Wizard apprentice 500 years past who was lost to the Queste.

Manila Standard said that his character comes off as an intriguing boy, who is taught early on to live cautiously (in his Young Army days), yet he longs for the love and affection of a family.

Also, the ease with which they dispatch their enemy, takes away his glory a little but also "this very element, makes for light and humorous reading and renders the children more identifiable."

She also said that Septimus was quite identifiable when compared with real world and comes off like the most intelligent but quiet boy in class whom we see at every school.