Danyal Hussein, 19, killed Bibaa Henry, 46, and Nicole Smallman, 27, after using his own blood to sign a pact with mythical demon King Lucifuge Rofocale, the Old Bailey heard.
In a “campaign of vengeance” Hussein pledged to kill six women every six months to win the Mega Millions Super Jackpot of £321 million and carry on killing women as long as he was able, jurors heard.
In another sinister note, he offered blood to ‘demon Queen Byleth’ to make a girl at his school fall in love with him.
Hussein’s killing spree was halted because he cut himself during the frenzied attack on the sisters, enabling police to track him through DNA.
Hussein was found guilty on Tuesday of two counts of murder and possession of a knife after a jury deliberated for around eight hours.
He stood facing the jury, crossed his arms and shook his head as the verdicts were delivered in front of the victims’ sobbing parents.
In a victim impact statement read to court, the sisters’ mother, the Venerable Mina Smallman, said she had “never come across such evil”.
The retired cleric said: “No one expects their children to die before them but to have two out of three of your children to be murdered on the same night is just incomprehensible.
“If any good comes out of this, had he not been found, he had another four women lined up to murder to meet his pact with his so-called demon.”
Mrs Smallman, who was the Church of England’s first female archdeacon of black and minority ethnic descent, made no bones about her past complaints with police as she commended the officers who brought Hussein to justice.
Speaking outside court, she said: “This team moved heaven and earth to ensure we felt that we were being supported.
“This is the kind of police force that I believe in and we need to work towards so we have justice and families are treated with respect.”
She added: “Today we remember our girls as the wonderful, strong women they were and we hope that some good will come out of this horrible story.”
Detective Chief Inspector Simon Harding praised the dignity of the victims’ family throughout.
On the verdicts, he said: “We are glad the jury saw through Danyal Hussein’s ridiculous denials of the overwhelming evidence in front of him.”
“I firmly believe he would have carried out his contract. He would have carried on killing women, until he had killed the first six. If he had not won the lottery by that stage – every six months is what he said.”
Jurors were not told of the extent of Hussein’s obsession with demons, spells and potions.
It can now be reported that he had come to the attention of police aged just 15 over fears he was vulnerable to radicalisation and violent extremism.
He had been on a de-radicalisation programme between October 2017 and May 2018 after being referred to the Prevent scheme by his school.
Following his arrest, police found Hussein had communication with others about demons and love potions, and carried out online research about the far-right and Norse mythology.
Police said they could not rule out a racist element to the selection of Hussein’s victims.
The trial had heard how Hussein prepared for the killings by buying a set of knives from Asda, a black balaclava on Amazon and signing up to a lottery betting website.
In the early hours of June 6 last year, he stalked his victims as they celebrated Ms Henry’s birthday in Fryent Country Park in Wembley, north London, laughing and dancing with fairy lights.
Hussein took Ms Henry by surprise, stabbing her eight times, before he slashed Ms Smallman 28 times as she bravely fought back, sustaining multiple defensive injuries.
Hussein dragged them by the feet into bushes where they lay undiscovered for 36 hours, their limbs entwined.
During the savage attack, Hussein cut his right hand with the 12cm knife which he dropped in the grass.
He attempted to clear the scene and disposed of the sisters’ mobile phones in a pond before returning to his father’s house in Wembley just after 4pm, without his trousers.
Over the next 10 days, Hussein spent £162.88 on lottery tickets and bets – all without success.
On the evening of June 6, the sisters’ worried loved ones reported them missing but officers were not deployed to the park until the next day.
Before police arrived, Miss Smallman’s frantic boyfriend Adam Stone, who could not believe she would have left their pet bearded dragon unattended, began searching the park with his parents.
He was on the phone to police when he found the bodies at around 12.30pm.
Mr Stone broke down in court as he told how he ran into bushes and fell to his knees before his girlfriend’s body after his father found a knife in the grass nearby.
Officers, who carried out a painstaking search, identified blood stains on the knife, bodies and surrounding scene all linked to the DNA of an unknown male.
The national DNA database failed to identify the sample but on June 30, in a major breakthrough, a DNA familial link was made to Hussein’s father, who had a past caution.
Within an hour and a half, pieces of the puzzle came together with Hussein being identified on CCTV buying knives in Asda and returning home after the murders.
Following his arrest, Hussein, who is of Iraqi Muslim decent, told police he had Asperger’s syndrome and trouble with his memory, then refused to answer questions.
Searches of his bedroom at his mother’s house in south-east London uncovered a book of spells, handwritten demon symbols and the two blood pacts.
Hussain disputed the overwhelming evidence against him but declined to go into the witness box. He was remanded into custody to be sentenced on September 22.
Two police constables have been charged with misconduct in public office after allegedly sharing pictures of the crime scene on WhatsApp and are due to enter pleas later this month.
Separately, the Independent Office of Police Complaints is investigating over the response to the initial missing persons reports.