Maiden of the Sun, Maia of Eru

Arien was originally a spirit of fire whom Melkor failed to corrupt. In the days of the Two Trees, Arien was a Maia maiden who tended to the golden flowers in the gardens of Vána. She would water the flowers of Vána with dew gathered from the golden tree Laurelin.

After the destruction of the Two Trees of Valinor by Melkor, Laurelin managed to produce one last golden fruit before it died away. Aulë crafted a vessel to hold the golden fruit. Arien was chosen by the Valar to guide the vessel of the Sun above the airs of Arda to give light to the World; Tilion, another Maia and one of Oromë's hunters, was chosen to steer the Moon. The Moon had already traversed the sky seven times before the Sun was finally ready. The first dawn of the Sun was like a great fire glowing upon the towers of the Pelóri Mountains of Aman. Morgoth was dismayed, and he descended into the uttermost pit of Angband and his servants withdrew. He sent up dark clouds of smoke to conceal his land from the light of the Sun.

Tilion loved Arien and followed her through the night sky. When he occasionally caught up to her, his vessel became singed by her heat.

Morgoth feared Arien. Some writings claim it was her fire that charred his armor black.

Arien, or some part of her, may have taken shelter in Aragorn's ring, which may be Narya.