Scorpius Malfoy
Son of Draco Malfoy. Scorpius is a Slytherin, though he is sweet, geeky, and more of a follower than a leader. After a rumor circulates that he is the son of Voldemort, Scorpius is marginalized by the rest of the Hogwarts students. However, he has one friend, Albus Potter.
Professor Minerva McGonagall
Headmistress at Hogwarts during Albus Potter’s years at Hogwarts.
Madam Hooch
The first-year flying teacher.
Cedric Diggory
A Hufflepuff student when Harry Potter studied at Hogwarts School of Witchcraft and Wizardry. Cedric was one of the competitors of the Triwizard Tournament but was murdered by Lord Voldemort shortly after winning. After Albus and Scorpius made sure that Cedric lost the Tournament, Cedric became an angry man. His anger turns him into a Death Eater, and he later kills Neville Longbottom.
Amos Diggory
Cedric Diggory’s father, now an old man. Amos always blamed Harry for the death of his son, and with his niece and caretaker, Delphi, decide to pay Harry
Potter a visit. Amos asks Harry to go back in time and save his son from being killed back in 1995.
Lord Voldemort
The most powerful, evil sorcerer in the wizarding world. When Harry was a baby,
Voldemort entered his home in Godric's Hollow to kill him. However, the love of
Lily Potter caused the killing curse to rebound to Voldemort, killing him instantly. After the third Triwizard Tournament, Voldemort was resurrected by using Harry Potter’s blood. A couple of years later, the Battle of Hogwarts occurred and Harry Potter defeated Voldemort.
Delphi
Though she appears as an awkward, clumsy caretaker of Amos Diggory, she is in fact the daughter of Lord Voldemort and Bellatrix Lestrange, born before the Battle of Hogwarts. Delphi is an orphan, similar to her father. Delphi used the Confundus Charm on Amos Diggory in order to pass as his niece.
Severus Snape
Potions Professor at Hogwarts who was murdered by Voldemort during the Battle of Hogwarts. Snape devoted his life to Albus Dumbledore after the death of Harry's mother Lily Potter at Voldemort's hands. He turned spy for Dumbledore and became a Death Eater, and was eventually killed by Voldemort. Harry considers Snape to be one of the bravest man he ever knew. Albus Severus Potter is named after Severus Snape.
Albus Dumbledore
Former Hogwarts headmaster who was killed by Severus Snape before the Battle of Hogwarts. Dumbledore played a paternal role in Harry’s life. In the play, Harry talks to Dumbledore via portrait, telling Harry that love has blinded him.
Polly Chapman
Hogwarts student. In the timeline of the Scorpion King, Polly asked Scorpius if he would go with her to the Blood Ball.
Trolley Witch
Hired one hundred and ninety years back when the Hogwarts Express first began. She sells sweets on the trolly, but her job description also includes making sure every student arrives at their destination.
Petunia Dursley
Harry Potter’s aunt. After James and Lily Potter were killed by Lord Voldemort, Petunia received the custody of Harry Potter, being Harry’s only relative. She always detested magic.
Dudley Dursley
Harry Potter’s spoiled cousin.
Vernon Dursley
Harry Potter’s uncle and Petunia’s husband.
Hagrid
Keeper of Keys at Hogwarts. On the night of James and Lily Potter’s death, Hagrid delivers him to live at Privet Drive with the Dursley's on Dumbledore's orders.
Dolores Umbridge
A Ministry bureaucrat and loathed Hogwarts professor in Harry's day, she is presently serving in Azkaban. When the past is changed, she becomes the Hogwarts headmaster after Harry Potter and members of Dumbledore’s Army are killed. She demands order and respect even from Scorpius. In the end, Umbridge discovers Snape and Scorpius's true allegiance, and she begins to attack Snape, but he defeats her.
Moaning Myrtle
Full name Myrtle Elizabeth Warren, a former student at Hogwarts. She was killed in 1943 by a Basilisk on the orders of Tom Riddle (Lord Voldemort). Her ghost haunts the girl’s bathroom, where she was killed.
James Potter Sr.
Harry Potter’s father who died protecting his wife and son from Lord Voldemort.
Lily Potter
Harry Potter’s mother whose love protected him when Lord Voldemort cast a Killing Curse.
Viktor Krum
Durmstrang student who participates in the Triwizard Tournament in 1994. Viktor was Hermione’s date to the Yule Ball.
Bane
A centaur who has philosophical Divination skills, he is protective of the Forbidden Forrest. He tells Harry Potter that there is a dangerous cloud around Albus Potter.
Ludo Bagman
The Triwizard Tournament moderator
Craig Bowker Jr.
A Hogwarts student killed by Delphi
Astoria Malfoy
Draco Malfoy’s wife and mother to Scorpius. During Scorpius's third year at Hogwarts, Astoria dies due to an illness.