Steadily becoming a saint, the immortal officials hired me to tend the horses

As a house servant, Gu An accidentally shattered a jar of Spirit Flowers in his youth, and in his panic, he discovered that he had seized twelve years of life span!
A path to immortality thus unfolded before Gu An's eyes!
In order to cultivate in peace, Gu An chose to become a Servant Disciple of the Supreme Sect, planting medicinal herbs daily to cultivate by seizing the life span of these herbs.
Through the evolution of life span, his Basic Skill constantly evolved, deducing from Basic Sorcery to reach Divine Skills that connected to heaven!
Eras changed, constellations shifted, and the Mortal World transformed vastly.
Gradually, legends of immortals emerged in the Mortal World.
The immortal known as Gu An expended half of his life span, helping his Cultivation Level break through the limits of the Immortal Path and achieving the realm of a Saint, soaring above the heavenly laws.
However, one day, a white-robed old man with a saintly presence came to visit Gu An.
"I am Xuan Qing from the Heavenly Stars above, appointed by the Heavenly Emperor Tai Hao. Hearing of Daoist Friend's numerous benevolent deeds in the Mortal World and your countless rescues of the living beings here, the merits are immeasurable. Thus, I have been dispatched from the Lower Realm to invite Daoist Friend to join the ranks of the immortals, to take up an immortal office, the Divine Steed Celestial Official."
"May I ask what the duties of the Divine Steed Celestial Official are?"
"In the Heavenly Court, there are divine steeds that can traverse earth and heaven and penetrate Yin Yang. The Divine Steed Celestial Official is responsible for looking after and feeding these divine steeds."
Huh? Taking care of horses? Groom?!