"She had to be sacrificed for our wishes," Lester Moody told the court.
He said the four wishes were power, wisdom, fame and money.
Moody, who admitted to setting Theologo on fire in 2011, was testifying against four other people implicated in the crime.
Lindon Wagner, Robin Harwood, Harvey Isha and Courtney Daniels have pleaded not guilty to charges of murder, attempted murder and assault to cause grievous bodily harm.
Moody and Jeremy King admitted to the crime. They were both sentenced to 17 years in prison, five of which were suspended.
Moody said the group had planned to burn candles on the corners of a satanic star.
"Then there was these papers [where] Lindon had written a few words that we were to say at the scene."
They would then make their wishes, and sacrifice Theologo so the wishes would come true.
When Wagner returned from work on Friday, 21 October in 2011, he told him they would sacrifice Theologo that night, Moody said.
Planning the sacrifice
Earlier he said the group had met on Thursday at Daniels' home and agreed the sacrifice would happen in about three weeks.
That day he played a game with King and Wagner in the kitchen at Daniels' home.
The game, which involved toilet paper and match sticks, instructed them that Theologo had to be sacrificed.
"We asked the game if Kirsty should be the prostitute and it said yes." This was to act out Revelations 17:16 from the Bible.
Moody said he read the verse repeatedly and it had left him confused. When asked what the verse said, Moody at first seemed to have forgotten, but then recited it.
"You know it off by heart?" asked the judge.
"Uh... eventually it got into my head," he replied.
Moody said they had not discussed the verse with Theologo but she came to the kitchen and said she should be sacrificed.
"She said we should drink her blood, eat her flesh, strip her naked and burn her with fire."
Theologo had apparently said this three times before; twice when she had been drinking and again when she was sober.
"In my point of view, she was serious," Moody testified.
He said although Kirsty had said she was the prostitute to be sacrificed, they did not tell her they were planning to kill her.
Drinking blood and eating flesh
Moody said Wagner told them what part of the sacrifice each would perform, but nothing was said about how Theologo would be set alight.
They agreed Moody would drink her blood and King would eat her flesh.
He said, according to their plan, Theologo would be drugged with brake fluid to make her dizzy, and all the acts would be performed while she was alive.
The court heard the accused had candles, a knife, a bottle of alcohol and brake fluid.
Moody said Wagner sent Isha to buy petrol on their way to the hill.
Theologo, her friend and the rest of the accused waited for Isha from across the road.
He told the court that at the time Theologo was told Isha was going to buy sweets.
Moody said Theologo was told the group were going to a party.
On their way there it was decided the group would go up to the mountain instead.
The trial continues.