Shinryu, later named after a legendary beast that the Domans know from Far Eastern legend, was created by the final actions of Ilberd Feare. Receiving the Eyes of Nidhogg from Elidibus, who deemed him an ideal user of the dragon's power, Ilberd orchestrated the slaughter of his subordinates when they take Baelsar's Wall to use their dying faith and aether to form Shinryu's body and repeat Nael van Darnus's intentional act of invoking a new Calamity. Ilberd committed suicide to complete the ritual, the frozen eyes of Nidhogg reacting to the man's despair and rage while absorbing the surrounding aether to give Shinryu shape atop Baelsar's Wall. Before it could fully take shape, Papalymo Totolymo sacrificed himself to seal the primal in a cocoon of light using Louisoix Leveilleur's spell.
Even sealed in the lucent cage, Shinryu's terrible might could barely be contained, as a Garlean airship that approached the cocoon was witnessed to be destroyed by a "lance of light." On the advice of Nero tol Scaeva, the Warrior of Light accompanies Cid nan Garlond, Yda Hext, Yugiri Mistwalker, and Gosetsu Everfall to the Carteneau Flats to reactivate the ancient Allagan superweapon Omega and use it to contain Shinryu. By then, due to the cost of maintaining the seal, Papalymo's life ends and Shinryu breaks free as Omega approaches Baelsar's Wall. A titanic clash ensues between the two that floods sections of the wall. The immense struggle ends with an explosion of light caused by Shinryu's Protostar attack colliding with Omega's Wave Cannon. Both primal and superweapon were last seen falling a distance away, both now being sought by the Garlean Empire.
No myth made manifest, this -- but a being of pure violence.Zenos yae Galvus to the Warrior of Light
After the Warrior of Light and their allies defeat Zenos in the Hall of the Griffin in Ala Mhigo, Zenos is enthralled by their previous battle and desires to take their final contest to the Royal Menagerie at the high point of the palace. The heroes give chase to Zenos, only to arrive to see Shinryu imprisoned in a magitek field behind Zenos. Zenos, ecstatic about the primal's means of creation, begins to taunt the Warrior of Light and questions what they would do should he release the so-called eikon. The Warrior of Light answers Zenos's question, only for him to respond that the adventurer does not have full mastery of their Echo and how he learned that the power can be instrumental in binding eikons to one's will. Zenos destroys the cage holding Shinryu and sets the creature free. However, by using his abilities as a Resonant, Zenos merges with Shinryu, with his consciousness overtaking the primal's body, and flies off to the airship landing of the palace.
Once the Warrior of Light arrives at the airship landing, Zenos destroys the bridge, leaving a single pillar for the hero and their allies to combat the primal. After summoning multiple smaller variants of the primal to combat the heroes, Zenos enchains the heroes in an attempt to defeat them with Shinryu's Dark Matter attack. The Warrior of Light and their allies break their bindings and avoid the attack by grabbing onto Shinryu's tail, which sends them to a battlefield high up in the heavens. After a climactic final encounter, Shinryu is defeated by the Warrior of Light and disintegrates, ejecting Zenos from the primal and leaving behind the Eyes of Nidhogg. The Eyes are subsequently destroyed by Estinien Wyrmblood.
Some time later, after observing the original form of Midgardsormr within Omega's databanks, Cid nan Garlond theorizes that since Shinryu's appearance did not originate from any belief system, it may have been derived from ancient depictions of Midgardsormr—the progenitor of all dragons on Hydaelyn.
Shinryu is the Japanese on'yomi name for Shénlóng, literally "god/divine dragon", an important ancient dragon in Chinese mythology. It is said to preside over storms and rain, and can bring disastrous drought, thunderstorms and general bad weather if it feels neglected and/or angered.
A notable difference between common Chinese dragons and a Shenlong/Shinryu is their fingers; the latter have five on each hand as opposed to four, and they are said to share the same green-blue-ish color as another mythological dragon, the Qinglong/Seiryu (lit. Azure/Blue Dragon).
While the most common Final Fantasy interpretations have four fingers on each hand, other versions also possess five-fingered hands like with the original Shenlong/Shinryu, which mainly apply to the stronger ones.