"Despite active work by our front-line staff to disrupt gang activities, prisoners go to great lengths to attempt to recruit members and carry out illegal activities in prisons," he said.
Te Runa was housed in Wing 35 - the "high-risk prisoner unit" - where inmates are only let out of their cells for up to four hours a day.
On April 24, the victim requested to share a cell with Te Runa and Corrections officers acceded.
According to court documents, the motivation for the move was that the man wanted to become a member of the gang.
He was to be Te Runa's apprentice and was in the early stages of prospecting, the court heard. But first he had to prove himself.
He had to be "conditioned".
The beatings started on May 6 and continued for nearly two weeks.
Te Runa would strike the victim all over his body, with a particular emphasis on the man's genitals.
"He was punched and kicked to his groin area including the insides of his thighs and testicles," a police summary said.
During the violent ordeal, the victim did not leave his cell and when prison officers did their rounds he covered his face and body with items of clothing and said he was fine.
However, on May 19 he was found with both eyes filled with blood. He had been punched in the jaw so often that his face was "swollen and unrecognisable" too, the court heard.
Bruises covered the victim's body and he was urinating blood before being admitted to hospital. Te Runa fractured two of the man's ribs and left him with haematomas to both thighs.
Counsel Anne Stevens said her client had pleaded guilty to injuring with intent to do grievous bodily harm at the earliest opportunity and had wanted to apologise to his ex-apprentice.
"He feels quite sick about what he did," she said.
In a pre-sentence interview, Te Runa said he derived no pleasure from dishing out the hidings and was ambivalent about his role as a Black Power enforcer.
"I accept there are expressions of remorse from you but I have to be a little bit circumspect about that," Judge Michael Crosbie said, pointing to the defendant's numerous convictions for violence.
"It's bad enough it took place within the prison environment - I understand prison is a difficult place - but this is not some type of dispute you had with someone that arose out of you being confined or sharing a cell. This was part of some long, drawn-out gang-related ritual and it needs to be condemned in the strongest terms."
Once Corrections discovered what was happening, Mr Miles said, Te Runa was placed in "directed segregation", reclassified as maximum security and transferred to Auckland.
"We have a duty of care to all prisoners in our custody, however it is very difficult to prevent violence from occurring when the people involved are complicit in concealing their behaviour," he said.
Because it was Te Runa's second strike offence under the three-strikes legislation, he will serve his entire term without the prospect of parole.
