The UFO expert, originally from Canterbury in Kent, travelled to Poland in July to give a talk on conspiracy theories, but was found dead on a sofa in the flat he was staying in.
Friends claim the 39-year-old, who went to the same school as Orlando Bloom, died in his Warsaw apartment after vomiting “black liquid”.
Authorities also insisted he died from natural causes but have yet to reveal the results of a post-mortem exam.
His heartbroken girlfriend Sarah Adams, 31, claimed he was being held against his will in Warsaw.
She said: “He was terrified, he wanted to leave.
“He said he was trying to get away from them.
“They were doing very dark black magic and satanic rituals to ‘de-programme’ him and get rid of demons.
“He said they had given him something that had put him in a coma for two days.”
It comes after his mother, Vanessa Bates, 63, said she suspected her son was murdered.
She said: “These people [who Max was mixing with] appeared to be involved with some very dark and dangerous areas of the world.
“I was afraid that as he was gaining popularity and fame that perhaps someone would want him out of the way, i.e. not alive any longer.
“I believe somebody”s killed him.”
Ms Bates received a text message two days before he died, which said: “Your boy”s in trouble. If anything happens to me, investigate.”
It was also claimed Mr Spiers was set to uncover a major government cover-up.
His mother added: “He was making a name for himself in the world of conspiracy theorists.
“But I think Max had been digging in some dark places and I fear that somebody wanted him dead.”