Isildur was instrumental in forging the Northern and Southern Kingdoms, and his line extends to the time of the Lord of the Rings trilogy through Aragorn, his heir.
It was Isildur's pride that allowed Sauron to rise again, as he had a chance to destroy the Ring, and was urged to by the Elf-Lord Elrond. Nevertheless, he decided to keep it; writing "It is precious to me, even though I buy it with great pain. Forever shall my house be bound to its fate, to never allow any hurt to the Ring." He was later betrayed by it, and killed by a band of Orcs.
