https://www.icy-veins.com/ffxiv/dragonsongs-reprise-ultimate-guide-for-dragonking-thordan
Dragonsong's Reprise (Ultimate) Guide for Dragonking Thordan - Final Fantasy XIV - Icy Veins
This page contains an in-depth guide for the high-end Duty Dragonsong's Reprise (Ultimate) specifically for Dragonking Thordan portion of the encounter.