The Thousand-Year Kingdom I Created: A Genius Mage’s Free and Easy Reincarnation Power Fantasy.

Leticia, the great magician, defeated the evil dragon and saved the world, then died, leaving behind a barrier that will last for 1,000 years. After her death, God heard her wish and she replied, "I want to live an ordinary life in the next life." 200 years later, Leticia is reincarnated as a skinny girl who is imprisoned and abused by beastmen. After regaining her memories of her previous life, Leticia is furious at God for bestowing such a cruel fate on her, far from ordinary. Furthermore, when she meets God again, he tells her that another evil dragon is about to be born... This is a fantasy that depicts Leticia's second life as she travels while hiding her cheat abilities.