Although there are several oases in the deserts of Solhara, The Oasis is the one located at the Southwestern most space of the continent. It is the home of the Powhatans, a native resilient people who do not take kindly to invaders. The land is blessed by the Green Man with a sentient willow tree who has been named Grandmother Willow by her people. It is her greatest warning to her people that only despair awaits them beyond the Oasis. It is rumored that 'Willow' is the heart of the Oasis and should something happen to her, the land would lose its blessing.
The Oasis was created in 200 AH, but the Powhatans--or any humans--didn't begin to inhabit this lush area until 280 AH. Two willow trees were the first sentient beings to take root shortly before the land was blessed by the Green Man, but they did not begin as trees.
Gaia, the elemental of Earth, and Sage the Green Man fell in love with one another well before the Great War was a thought. Willow was born the product of her parents' love but was kept hidden from the rest of the Pantheon due to the laws against demigods. Although the Great War had Gaia and the Green Man fight on opposite sides, they never stopped loving each other, and he purposefully turned a blind eye when she fled the punishment the other Elementals and Seasons received before banishment to Allutheria. He knew how to find her, and they continued to leave subtle messages for one another in the element of earth and plants they shared. Helios the Lightgiver discovered the noncompliance and sought to punish Gaia herself, but the Green Man defied him.
Before the fight could escalate any further, Gaia turned herself and her daughter into willow trees as an act of surrender. It was not enough for the Lightgiver until the Green Man tied their essence to the earth, thus blessing that patch of land and forming the Oasis. Only with the condition of 'So long as the sun rises in the east and sets in the west, they shall never leave this land' was the Lightgiver finally appeased. Gaia understood that should she step foot outside of the Oasis, her life was forfeit.
The Oasis existed in solitude with just Gaia and Willow in the company of one another and various animals that had found their way there. Decades later, Gaia woke one night to find her daughter's tree missing before feeling the swell of a boost of power course through the Oasis. Willow had crossed the boundary into the desert beyond, thus ending her short life.
The Green Man answered Gaia's call but was unable to do anything for their daughter. It was too late to rescind the vow made to the Lightgiver. The Green Man knew he could not leave Oasis in solitude forever, however, so he sought companions for her and found the Powhatans. As they were devout followers of the laws of nature, he knew they would respect the land given to them so he led them back to the Oasis. Gaia was introduced to them as 'Grandmother Willow' and became protective over her new children, constantly warning them against leaving the land for she could not protect them beyond its borders.