The Oath is the fifth chapter of The Castle of Llyr. Here the themes of oath-taking and well-intentioned blundering are developed, by making the pledge onerous, and linking it to the frustration of enduring another's repeated errors.

This page contains spoilers. If you do not wish to be spoiled, do not read further.
When Magg and Princess Eilonwy failed to show for breakfast, Taran decided to break his silence and reveal Gwydion's warning about Achren's scheme of revenge. King Rhuddlum organized search parties, one nominally under the command of Prince Rhun, with the Master of Horse truly in charge.
Welsh king
As the bards already sang of Taran, Rhuddlum asked him to protect Rhun personally. Rhun must rule one day as King of the Isle of Mona, and Rhuddlum confided that he and Queen Teleria had long hoped for Rhun's wedding to Eilonwy.
Although appalled and envious, Taran took the oath to protect the Prince. On the search for Eilonwy in the Hills of Parys, Rhun separated from the group shortly before dusk. Taran pursued him, joined by Fflewddur and Gurgi, but finally the trio had to halt and spend the night in the forest.
The Castle of Llyr
1. Prince Rhun | 2. Dinas Rhydnant | 3. The Shoemaker | 4. Shadows | 5. The Oath | 6. The Potions of Glew | 7. The Lair of Llyan | 8. The Harp of Fflewddur | 9. The Luck of Rhun | 10. The Cavern | 11. King of the Stones | 12. The Tomb | 13. The Ladder | 14. The Empty Book | 15. The Island | 16. A Meeting of Strangers | 17. The Spells of Caer Colur | 18. The Golden Pelydryn | 19. The Flood | 20. The Pledge
Community content is available under CC-BY-SA unless otherwise noted.