A knife attack in a Norwich flat only stopped after the victim's sister screamed at her brother's attackers that they were 'going to kill him' if they carried on.
The victim needed a blood transfusion after being stabbed in the leg when he was attacked by three youths at a flat in Jewson Road.
He had been set upon by a group of young men on September 28 last year, but they returned armed with weapons to carry out a second, more serious attack.
David Wilson, prosecuting at Norwich Crown Court, said Brandon Green, now 19, Connor Farley, now also 19, and Leon Jones, now 18, were involved in a "joint enterprise attack" against the victim.
During the second attack, Mr Wilson said Green stabbed the victim "around 10 times with a knife".
Green also used a plant holder to hit the victim, whose sister was also attacked herself as she "tried to protect him".
The ordeal only "came to a halt" when the victim's sister "screamed out 'you're going to kill him if you carry on'", the court heard.
Mr Wilson said the participants in the attack were "involved with the drugs scene".
Green, of Tuckswood Lane, Norwich, appeared for sentence on Monday (October 7) after being found guilty of wounding with intent and two offences of assault causing actual bodily harm following a trial in March.
Farley, 19, of no fixed abode, and Jones, 18, of Wingfield Road, Norwich, also appeared for sentence having both previously admitted wounding with intent and assault occasioning actual bodily harm.
Sentencing all three defendants Judge Alice Robinson said it was a "shocking incident of violence" in which the victim suffered life-threatening injuries.
She assessed all three defendants as dangerous offenders who all pose a significant risk of serious harm to the public and gave Green an extended sentence of 12 years custody and three years on licence.
Farley and Jones were each given extended sentenced of nine and a half years custody with three years on licence.
Michael Clare, mitigating for Green, said his client accepted he would receive a "substantial" prison sentence with a "long time" to mature.
Gavin Cowe, for Farley, said he had a "troubled" and "dysfunctional childhood" and had gone along, not because of a grievance, but to offer support.
Marc Brown, for Jones, said his client's main mitigation was his guilty plea but insisted while he was a "willing participant" he was a "subordinate" and has shown genuine remorse.
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