Illustrate an oil painting of an immortal goddess named Seraphina, encapsulating the youth, beauty, and timeless grace reminiscent of the romantic era, akin to the work of Pierre Auguste Cot. She should be portrayed with a radiant complexion that radiates immortality. The painting must focus on the intricate details of her soft, flowing attire, exuding an ethereal quality. Her hair should be styled in a timeless manner, and her eyes should reflect profound wisdom. The background should depict a tranquil, classic landscape that complements her divine aura.