In The High King, the final installment of Lloyd Alexander's Chronicles of Prydain series, Taran of Caer Dallben, the protagonist, is launched on a critical mission that tests his courage, loyalty, and the bonds of friendship. The book begins when Taran is presented with a letter from Prince Gwydion, sent through the enchanter Dallben. The letter reveals a threatening scenario: Arawn Death-Lord has acquired the destructive Black Cauldron and the powerful sword Dyrnwyn, presenting a significant threat to the entire kingdom of Prydain.
Upon receiving this news, Taran rallies his close-knit group of friends: the fiery-haired Princess Eilonwy, Fflewddur Fflam, the wandering bard and king, Gurgi, a simple but loving creature, and the dwarf Doli of the Fair Folk. They set forth on a perilous quest towards the Land of Death, Annuvin, to confront and defeat Arawn. They meet and engage with various characters as they journey through the treacherous terrains. The three crafty enchantresses Orddu, Orwen, and Orgoch test their resolve while the obstinate and arrogant Prince Ellidyr seeks the magical sword for his selfish motives.
As the companions inch closer to Annuvin, they face trials that bring out the hidden depths of their characters and test the strength of their bonds. Taran grapples with questions of self-worth and identity, his common birth in stark contrast with the nobility of his actions and leadership. Taran's bravery shines through in the climactic confrontation with Arawn, overpowering his self-doubt. He uses the powerful sword Dyrnwyn, finally able to wield it due to his selfless intentions, and vanquishes Arawn, freeing Prydain from his oppressive rule.
In the aftermath of this victory, Taran is faced with a profound choice. The immortals, including his friends, are leaving for the Summer Country, a land of eternal peace and youth. He could join them, living an immortal life, but without Eilonwy, who is mortal, cannot enter the Summer Country. Or he could stay in Prydain, mortal and aging, but with his beloved Eilonwy by his side. Taran's choice of a mortal life with Eilonwy reflects his growth from an ambitious youth to a wise leader who understands the value of human experiences and relationships. In the end, Taran is crowned as the High King of Prydain, concluding the series on a hopeful note that heralds a new era of peace and prosperity for Prydain.
