Of the charges, 24 included acts of serious sexual violations.
A jury found him guilty of eight counts of rape, 16 of sexual violation by unlawful connection, two charges of injuring with intent to injure, and one charge each of kidnapping and assault with a weapon.
Webster earlier pleaded guilty to two representative charges of male assaults female.
Crown prosecutor Justine Sutton read the impact statements, which described Webster as appearing nice at first, before turning nasty, violent, "controlling and manipulative".
One of the victims said giving evidence in court was "incredibly harrowing".
"... you are a monster who took away my sense of self-worth... I am standing here today to reclaim my confidence and power," the court heard.
Another victim said for years she believed the physical, emotional and financial abuses were her fault and she was too ashamed and embarrassed to talk about it.
She turned to drugs and alcohol to cope, the court heard.
Webster's offending included abducting one woman, taking her to a cell he had built and subjecting her to multiple rapes and other sexual abuses over several days. She suffered life-long injuries.
A third victim was subjected to brutal violence, including both physical rapes and other non-consensual sexual abuse, on multiple occasions.
She was hit, punched, choked and kicked, and told the court she felt she could never cleanse herself of the abuse she suffered.
Crown prosecutor Sutton told Justice Christian Whata the victims were subjected to "horrendous violence and sexual abuses" which spanned almost 20 years.
She submitted a sentence of preventive detention was warranted given the scale and gravity of Webster's offending and his assessed risk factors.
Webster was assessed by two psychologists as being at high risk of further physical violence and also at a "very high" risk of further sexual violence against women.
He also had an "extremely high" score on the sexual deviant risk assessment scale and preventive detention was needed to protect the community and to deter Webster from offending.
Webster continued to deny his crimes, she said.
Webster's lawyer Tony Rickard-Simms opposed preventive detention.
Despite the risk assessment reports, Webster was not a risk to the public; had not offended against children and had no prior convictions for these types of crimes, he said.
Rickard-Simms said while his client had maintained his innocence, rehabilitation programmes would be available to him.
Justice Whata said two health assessor reports were done about Webster, one of which found his offending appeared to be "driven by deviant sexual fantasies".
One stated Webster was "emotionally shallow" and avoided close intimate relationships, enabling him to "perform cruel and instrumentally violent sexual acts", he said.
The second report concluded Webster had a "demonstrable capacity for vengeance and sadistic cruelty and use of all types of aggression", the court heard.
Justice Whata said due to Webster's lack of remorse, his "egocentric outlook" and other concerning traits and risk factors, he was unlikely to benefit from treatment.
"The combination of the pattern of your offending, your trenchant denial of it, the very high risk of offending posed by you, mean that I consider preventive detention is necessary to protect the public from you," he told Webster.
"Your clear tendency to manipulate and then to grossly abuse your victims is not something I can be satisfied that will be addressed over time."
Along with Webster's preventive detention sentence, Justice Whata imposed a minimum non-parole period of nine years and five months.
