Shen-zin Su

Shen-zin Su is a great turtle that roams Azeroth's oceans, which some pandaren named the Wandering Isle on which they explore the world outside Pandaria. Not merely a gigantic turtle, Shen-zin Su is a fully sapient being and quite aware of the pandaren that have been living on his back for generations.

Birth and meeting Liu Lang
Centuries ago, a sea turtle hatched at Turtle Beach in the Krasarang Wilds, in the land of Pandaria. This turtle presumably lived a normal everyday life, reaching adulthood and becoming a creature of noteworthy size. One fateful day 800 years before the Dark Portal, it met and was befriended by a pandaren named Liu Lang.

Though pandaren lived in harmony with their native land, wanderlust has gripped a small portion of their hearts for as long as they can remember. To satisfy that wanderlust, to explore the world he knew waited beyond Pandaria's shores, Liu Lang wanted to have a way to leave Pandaria and yet be able to come back through the mists that hid the small continent. He came to realize that sea turtles always return to the beach where they were born, and thus he would always have a way back home.

Wanderlust
At this point, the sea turtle had no name. When Liu Lang bought his travel supplies at Halfhill from Shen-Zin, owner of Shen-zin's Sundries, Shen-Zin humored his announcement that he was going to explore the world by suggesting that he should take a bamboo umbrella and offered one, on the house. A grateful Liu Lang happily told the supplier that he would name his sea turtle after him.

Liu Lang would spend the rest of his life traveling with Shen-zin Su, making return trips to his homeland every five years, each time bringing with him stories of the wondrous things he'd seen. The turtle would prove time and again to have grown even larger from the last visit, eventually growing to the size of a giant island, large enough to support an entire colony and several villages.

On Liu Lang's final voyage to Pandaria, he fell into a deep sleep and died, his spirit merging with the sea turtle. Shen-zin Su stopped returning to Pandaria for generations, despite being able to do so if he wished. In fact, he avoids the mist where the island continent is located. While only Shen-zin Su truly knows the reason why, the pandaren of Pandaria presumed that Shen-zin Su stopped doing so shortly after the death of his beloved friend, Liu Lang.

The descendants of Liu Lang's followers, whom Shen-zin Su would dub the "grandchildren" of Liu Lang, still travel on the great turtle's shell to see the world. The turtle has continued to grow since Liu Lang's time to a truly massive size, supporting several villages, forest, and small mountain ranges. The settlers would appropriately call the sea turtle's shell "the Wandering Isle".

Cataclysm
During the Cataclysm, Shen-zin Su out at sea was hit with horrible waves, but it seems he was able to compensate for them and the pandaren were not unduly affected.

Mists of Pandaria
After the discovery of Pandaria, the great turtle was dragged by the Maelstrom. The gunship Skyseeker crashed into it, causing the great turtle to no longer swim straight. Realizing that the source of Shen-zin Su's pain is The Skyseeker a young pandaren adventurer and Master Shang Xi's disciples head into the forbidden Pei-Wu Forest. There, the party helps triage members of the Horde and Alliance, as well as fend off new horrors from the depths. Immediate threat taken care of, Ji Firepaw decides to blow up what's left of the Skyseeker. Shockingly, this plan actually works, to a point. Aysa Cloudsinger glares at Ji and walks away, leaving him looking sad but resolute, as Shen-zin Su lets out a groan of agony. Shen-zin Su now has a river of blood pouring into the sea and it's up to healers of both the Alliance and Horde to stitch him up, but not without what's left of the invading forces harassing the healers.

Legion
After the Peak of Serenity on Pandaria was destroyed by the Burning Legion, the survivors traveled to Shen-zin Su, who happened to be close by.

Battle for Azeroth
As the War of the Thorns began, spurring the Fourth War, Shen-zin Su was swimming towards the Broken Isles, as the pandaren living on his back heard that it's relatively safe to explore now.

Notes and trivia

 * Originally the cause of Shen-zin Su's stress was the Maelstrom, as recounted in this pre-release quote: "When Shen-zin Su travels near the Maelstrom, life on the Wandering Isle—once pacific and enlightening—is cast into crisis. The ground becomes unstable and Shen-zin Su's very life is threatened as the great turtle drifts into an unsteady pattern which may be a death spiral."
 * According to the Pet Journal entry of the Emerald Turtle "it is difficult to believe that Shen zin Su [...] began life as a tiny emerald turtle." While the Wanderer's Festival Hatchling says "Legend has it that a seadragon turtle just like this one grew up to become Shen-zin Su [...]". Chronicle Volume 1 describes him as a sea turtle.
 * Both of those types of turtles have feet, while Shen-zin Su has flippers.
 * The original plan for the origins of the Pearl of Pandaria was to have Shen-zin Su swallow it when he was young. This was later scrapped in favor of the pearl belonging to a tribe of murlocs.
 * As he was already a very large adult when he met Liu Lang, as of Warlords of Draenor he was probably somewhere around 850 years old.
 * Arguably, Shen-zin Su is the largest animal in Azeroth, possibly the largest animal known to exist so far.
 * Shen-zin Su is voiced by Jim Cummings in The Suffering of Shen-zin Su.
 * Shen-zin Su is most likely a reference to the general mythological concept of the World Turtle, a giant turtle that supports the entire world on its shell.
 * Shen-zin Su's oversized fins can sometimes be seen swimming alongside the main body of the Wandering Isle.
 * Shen-zin Su ( 神真子, Pinyin: Shénzhēn Zi ) is Chinese for "the true, godlike Sage."