Steven Wylie (28) had 20 months added to his sentence at Hamilton Sheriff Court this week.
He admitted making threats at HMP Perth in October last year and starting fires which damaged cell fixtures and fittings at HMP Shotts in June and July last year.
Wylie was jailed for three years and two months in September 2016 after he and an accomplice burst into a pensioner’s caravan in Straiton.
The 76-year-old woman was terrified by the masked men who were looking for drugs they believed had been hidden there without her knowledge.
Earlier that year Wylie was handed a 23-month prison stretch for offences including theft and dangerous driving.
In the latest case, Shotts guards raced to Wylie’s cell in a segregation unit when an alarm went off about 10pm on June 24 last year.
Vish Kathuria, prosecuting, said: “He was removed from the cell and treated for smoke inhalation.
“There were matches and paper in his cell. Officers could see the fire had been started deliberately. Fortunately, it didn’t spread.”
Mr Kathuria said a sprinkler system was activated when another late night fire was started at Wylie’s cell on July 30 last year.
He added: “Again, staff could see it had been started deliberately.”
By October, Wylie had been moved to Perth and on Hallowe’en guards went to search his cell after intelligence suggested he had an illegal phone.
The fiscal went on: “He was searched and moved to a segregation unit, but he became extremely aggressive towards the prison officers.
“He shouted ‘You f....rs’ are going to regret this. The first opportunity I get I’m going to do you. I’m going to f...… murder you and your families.”
Wylie’s lawyer said he’d been taking illicit valium at Shotts and had little recollection of the fires.
The solicitor added: “He wasn’t aware of the first fire at all until he woke up in hospital.
“He’s been having psychotic episodes and is now on medication. He’s spent all but two months of his current sentence in segregation.”
Wylie was due for release next July, but will now spend a significantly longer time in custody.
Sheriff Marie Smart jailed him for a year for what she described as “serious” threats towards the Perth guards.
He got eight months in total for the two fires, to be served consecutively.
The sheriff told him: “I take account of your guilty plea and you will be given the maximum discount. That means a 30-month sentence is reduced to 20 months.
“It will start at the expiry of your present sentence.”