Peter Moore said he still loved "Jason", whom he last saw nine months ago in the public gallery of the court where he was taken to face the murder indictment.
He bought time for Jason to escape by making confessions to the police, Mr Moore said under cross-examination. And he warned that Jason would kill again.
Mr Moore, 50, entered the witness-box at Mold Crown Court to admit he was a homosexual who derived pleasure from painful humiliation of partners. But he had never killed or caused serious injury.
In late summer last year, Mr Moore told the jury he met Alan Williams, a 48-year-old hotel worker. They became lovers, and Mr Moore coined a term of endearment - "Jason" was the character in the Friday the 13th film series who killed with a knife.
Mr Moore denies murdering Henry Roberts, 56, of Anglesey; Edward Carthy, 28, from Birkenhead, Merseyside; Keith Randles, 49, from Chester; and Tony Davies, 40, of Colwyn Bay. All were stabbed to death between September and December, 1995.
The prosecution has claimed that Mr Moore, of Kinmel Bay, Conwy, admitted in detail to the murders during interviews by detectives lasting more than 13 hours. Only when questioning was about to end did Moore claim another man was involved.
Mr Moore told the jury he bought Jason a pounds 25 combat knife as a gift. He said he was at the scene of three killings, but did not participate in any. He had tried to stop Jason, but, on one occasion, he was forced by him at knifepoint to drive to the scene of a murder.
The last killing was the first Mr Moore witnessed. He told the jury that he and Jason had been discussing a business partnership. They had parked at a beach popular with gays when Mr Davies arrived and walked to the water's edge followed by Jason. Mr Moore said he went to the beach because he was worried for the man's safety, but his shouted warnings came too late.
Mr Moore broke down as he told the jury: "I kneeled down and I held his hand. He said he loved his wife and he'd got two children ... and then he gave a sigh, and he died on the beach. He died in my arms."
Mr Moore said he later fought with Jason, and added: "I don't know where he is now."
The trial continues.