- "No interviews without appointments except between nine and ten p.m. on second Saturdays."
- ―Gumpas (Chapter 4) [src]
Caspian's Telmarine predecessors had discouraged maritime trade and commerce, and paid little attention to their overseas territories. By the time Gumpas had become governor, he and his predecessors had grown used to ruling without Narnian interference. Lord Bern had explained to Caspian that, "all is done in the King's name. But [Gumpas] would not be best pleased to find a real, live King of Narnia coming in upon him."
Gumpas is described as cowardly and dishonest, who ruled the islands in a bureaucratic fashion, and laziness and ill-discipline had become the hallmarks of the local government. During the years of no contact with Narnia, friendly relations with Calormen were pursued, and the Islands had become the centre of a burgeoning (and illegal, under Narnian law) slave trade.
When Caspian was captured by a band of kidnappers and slavers, led by one Pug, he was purchased by Bern, but immediately set free upon the latter discovering his identity. Outraged by all aspects of the situation, and learning that the Governor was colluding with the slavers, Caspian tricked Gumpas into believing that a large Narnian fleet was present, and, with Bern and a number of soldiers from the Dawn Treader, visited him in Narrowhaven Castle the next morning.
Gumpas notoriously refused Caspian an interview without even looking up, but was forcibly removed from the vice-regal chair. Caspian pointed out that Gumpas was personally liable for 150 years' worth of the tribute due to Narnia from the Islands, and insists over Gumpas' protests that he take action to stop the slave trade. When Gumpas refused, Caspian immediately dismissed him.
- "I think we have had enough of governors."
- ―Caspian (Chapter 4) [src]
Caspian then abolished the office of governors, as he had had enough of them, and appointed Bern as Duke of the Lone Islands.
Gumpas was then forgiven for his debts with the overdue tribute, but was given one day to vacate Narrowhaven Castle.
Of his later life and eventual death, nothing is known.
Gumpas was described as a bilious-looking man, with hair that had once been red, but had by then turned mostly grey.
He allowed him to capture people, sell some into slavery, and the rest they would sacrifice to the Green Mist. Gumpas was most likely the one who had had Lord Bern jailed years ago, and kept him there.
When Caspian visited Narrowhaven, he announced to all that he was their king, but Gumpas paid this no heed.
Whether this was because he didn't believe him, or because he simply didn't care, is unknown. He was present, though, at the selling of Lucy and Eustace at the slave auction.
When the crew of the Dawn Treader came and lead the islander's revolution against him and the other slavers, he tried to escape, only to be knocked out by Eustace of all people, when he was accidentally whacked across the head by him, knocking him into the water.