In the Series
In Magyk, Simon was first seen at the beach with his father and 5 brothers, reading in one of his father's old wizard books. When shooed away from the beach, he asked about wizards being the best. He is an ambitious and competitive boy who dreams about becoming an ExtraOrdinary Wizard. When the Heaps flee from the Supreme Custodian, Simon sneaks away to find his sweetheart, Lucy Gringe, and attempts to marry her but fails and gets locked away. He would occasionally talk to the Supreme Custodian trying to get information and giving him ideas about Darke Magyk. He escapes and reunites with his parents, brother, and sister just in time for Boy 412's Apprentice Supper, and the revealing Boy 412's true identity-Septimus Heap. Angry with the boy, saying that Boy 412 was not Septimus, for getting the Apprenticeship that he wanted, Simon ran off and found the bones of DomDaniel, and reviving him and becoming his new Apprentice.
In Flyte Simon kidnaps Jenna and wants to kill her. She escapes him and he sets his Tracker Ball named Sleuth after her. He attacks Jenna, Septimus, Nicko, and Wolf Boy on the Causeway and shows off his new gift of Flyte to them. Simon is also involved with a Darke plan to bring back DomDaniel. He puts a bone of DomDaniel in every piece of a ShadowSafe built to get rid of Marcia's troublesome Shadow. Marcia is able to survive, and Septimus gets Simon's piece of the Flyte Charm after he attempts to attack Septimus and Jenna while they are on Spit Fyre. Septimus saves Simon from a huge fall, and reunites his Flyte Charm with the one Marcia gave him when she asked him to be her Apprentice. In the end, Simon leaves the Castle.
In later books, Simon wishes he didn't get involved in Darke Magyk. He keeps trying to help Marcia or give her information, hoping that she will forgive him.
In Darke, Simon helps Septimus figure out where the entrance to the Darke Halls is, and gives him advice on how to get out. He also explains to Marcia how to get rid of the Darke Domain.
Before the events of the TodHunter Moon Series, Simon and Lucy have a son together, William.
During the events of Pathfinder, a blind transport infects Simon's right eye with Lapis Lazuli, filling the entire eyesocket with the magical blue stone, and possibly extending into his brain. The right eye was able to be infected due to an existing scar, which he received during Flyte, from Wolf Boy's slingshot.
Simon is very powerful Wizard. Though not quite as gifted as Septimus , he far surpasses the remainder of his family including his father, Silas Heap . After studying with DomDaniel , he also became a gifted user of Darke Magyk , becoming a Darke Wizard until he quit using Darkenesse in later books when he "turned Lyte."
Simon also became fairly good with the power of Flyte Charm however he never mastered it like Septimus because he lacked the complete Charm long enough to do so. He was able to,in Flyte, fly very high and attack his enemies from the air.
He also owns the Camera Obscura, after DomDaniel passed away at last, which he used for spying on the peoples of The Castle during his Darke times.
As noted by Septimus in Fyre, Simon possesses the same level of proficiency as Septimus himself, despite being largely self taught most of his more advanced skills and his younger brothers powers as a seventh son of a seventh son.