The Endless Sky Beast is a patron god of the Soaring Tribes. The Holy Beast has a look of a crimson flood dragon with an ox head. Its incarnation can be summoned with the flesh and souls of the two grade 7 Demon Beasts.
Endless Sky Beast sent an avatar to Mortal Realm, because of incoming tribulation. If it was unable to transcend that tribulation and its soul was destroyed, Endless Sky Beast would live as that avatar. Since the spiritual Qi is very sparse there, it makes it easier for it to avoid its great tribulation. Also, it would be more difficult for its enemies to learn its backup plan and destroy this avatar.
After Han Li caused a chaos for the Soaring Tribes, Saintess Lin Yinping performed a ceremony to summoning their Holy Beast's avatar. For next days, the Endless Sky Beast's avatar was chasing Han Li. After their Holy Beast sensed a body of the foreign cultivator moving in one way and a Nascent Soul travelling in another, the hunting party decided to split. Soon after Saintess and the Endless Sky Beast's avatar met Han Li and clashed with him. As he tried to kill the beast, she used a cauldron looking like his Heavenvoid Cauldron. The Saintess was shocked, when Han Li brought out a small cauldron similar to her own holy cauldron. After a struggle, Han Li seized her cauldron, sealed the Endless Sky Beast's avatar and escaped.
Endless Sky Beast's avatar gained intelligence and recovered most of its memories from its time in the Spirit Realm after spending 100 years in the Heavenvoid Cauldron. When Han Li reached the late Nascent Soul Stage and opened the cauldron, Endless Sky Beast's avatar tried to escape, but was unable to leave the cauldron.
The beast spoke for the first time, when Han Li was investigating the golden talisman of Patriarch Golden Flower. It also proposed to use Kun Peng Feather to refine Thunderstorm Wings into a Divine Spirit Treasure. Endless Sky Beast's avatar wanted Han Li's help with metamorphosis tribulation and to release it from the Heavenvoid Cauldron. Han Li agreed to that before he passes away or ascends to a higher realm. Then the beast's avatar was greatly shocked, when Han Li found a half of a page with beveled silver text from Golden Jade Tome in Patriarch Golden Flower's storage bag. Then it proceeded to explain that this item originated from the True Immortal Realm. During their travel, Endless Sky Beast's avatar taught Han Li characters of beveled silver text. After refining Thunderstorm Wings didn't go exactly as planned and Endless Sky Beast's avatar was in wrong, it helped Han Li with identifying some other materials and refining them.
After Han Li assimilated second Nascent Soul, he found a secluded place for Endless Sky Beast's avatar. It was to go through the metamorphosis stage tribulation. The beasts was grateful to Han Li for offering a drop of Glacial Quintessence. As the avatar withtood 11 waves of ferocious Heavenly Lightning with a bit of Han Li's help in the end, it transcended its tribulation. The avatar's human form looked similar to Endless Sky Beast's true body's human form, but it was a child. Later, back in Han Li's cave abode, they discussed passing through spatial node to the Spirit Realm and techniques, like Brightjade Arts.
Endless Sky Beast's avatar often shared his knowledge to Han Li and gave him refinement methods, but for something in return.
Dominating the Scattered Star Seas
When Han Li became the Guest Elder of the Star Palace, but didn't stay there taking over it, the Endless Sky Beast's avatar admired the firmness of his heart in his pursuit of the Great Dao and not a simpler power.
Endless Sky Beast's avatar and Han Li failed to move the Divine Essencefused Mountain, but the latter had an idea of refinig and using the Black Wind Flag. Endless Sky Beast's avatar proposed using other spatial treasure known as the Crimson Soul Flag. The beast wanted to help, because it was interested in the Divine Essencefused Light art.
After Endless Sky Beast's avatar helped decoding the information from the half-page of the Golden Jade Tome about a hundred years later, Han Li set free the avatar from the Heavenvoid Cauldron. After he sensed one of his brethren, he decided to go to them.
It is later implied that the Endless Sky Beast appears again, traveling with the Six-Winged Frost Centipede in the Heavenly Horse Plains. We see him hunting down a group of cultivators alongside the centipede, the strongest of which had a mid-Spatial Tempering Stage cultivation, for a treasure they possessed. This treasure, the Profound Yin Crystalline Wall, would help the centipede manifest a true spirit body.
Note: It is revealed much later that the Endless Sky Beast is a clone of Mouse Monarch Dong Tian from the Jade Mouse race who is one of the Seven Demon Monarchs of Spirit Realm.