Wikipedia
The Telmarines are a people in the fictional world of Narnia created by the British author C. S. Lewis for his series The Chronicles of Narnia. Hailing from Telmar, the Telmarines are prominent in the book Prince Caspian, the second book published in the series. The word "Telmar" may have been inspired by Latin tellus "Earth" and Latin mare "sea", since before they arrived in Narnia, the Telmarines were pirates in our world.
No scene from the books takes place there, but Telmar is said to be "far beyond the Western Mountains." According to the timeline drawn up by Lewis, Calormen extended west into Telmar some three centuries after the world was first created. However, after only two years, the Calormenes in Telmar behaved so wickedly that Aslan turned them into dumb beasts, and the area became effectively unpopulated. Pirates from our world arrived in Telmar over a century later, through a rare gateway between the worlds. Prince Caspian describes how the descendants of these pirates, the Telmarines, invaded Narnia many generations later, leaving Telmar behind and suppressing Narnia's native inhabitants. This led eventually to the events related in Prince Caspian.
Telmarine leaders of Narnia in Prince Caspian are King Miraz (brother of the late Caspian IX), Queen Prunaprismia, Lord Glozelle, and Lord Sopespian. In the film version of Prince Caspian, the principal Telmarine characters are portrayed by Spanish, Latin American, and Italian actors.
The high-ranking Telmarines are shown to be corrupt, scheming individuals. Miraz had his own brother killed in order to claim the throne. Sopespian and Glozelle plot together to kill Miraz and blame it on the Narnians in order to declare all-out war on them. This plan succeeds, although the Telmarine army is defeated in the subsequent battle, ending some 300 years of oppression (according to the timeline).