Driver of the Moon, a Maia of the Ainur created by Eru and, therefore, deathless.
Tilion, a hunter of the company of Orome, held a great love for silver; even his bow was of silver. At rest, he left the woods of Orome to go into the land of Lorien to dream by the pools of Este, in Telperion's flickering light. When Telperion was dying, Tilion requested the tending of its last Flower of Silver. Along with its vessel, the flower was called Isil, the Moon. As Telperion was the elder of the two trees, so was Isil the first of the two new lights rising into the realm of stars. At Tilion's coming, many things stirred and woke that had waited under the Sleep of Yavanna. The light filled the servants of Melkor with amazement, and the Elves of the Outer Lands with delight. As the Moon rose, Fingolfin blew his silver trumpets and began the march from the Helcaraxe to Middle-earth.
Tilion crossed the sky seven times before the advent of Arien. Seeing her, his own course became wayward and of uncertain speed. Drawn by her splendor, he tried to come near Anar so that he was scorched and the island of the Moon darkened.
Also around this time, Irmo Lorien, the Lord of Dreams, and his wife, Este, the Lady of Rest, asked Varda for help, saying that sleep had been banished and the stars hidden at all times. So Varda changed the course of the Sun and Moon, allowing shadow and half-light.
Arien with Anar therefore rested in Valinor in the cool of the Outer Sea, a time called Evening, the hour of greatest light and joy in Aman. Then the servants of Ulmo drew the Sun down, and Arien drove Anar in haste under the Earth coming unseen to the East there to rise again before evil could walk under the Moon.
Tilion with Isil was to do the same, arising in the East after the Arien had descended. However, Tilion still felt attraction to Arien, so that he may sometimes be seen in the sky with her and may come too close, cutting off her brightness with his shadow for a time. Also, he did not stay long in Valinor, but passed swiftly over Avathar or Araman or Valinor to plunge into the chasm beyond the Outer Sea, wandering long in the grots and caverns at the roots of Arda, returning late.
So, due to Tilion the Wayward, time was reckoned by the Sun by the Valar until the Change of the World.
Melkor attacked Tilion with spirits of shadow, but Tilion was victorious, having learned to fight mightily during his time with Orome.
After this, Melkor feared to attack Arien, and bound himself more tightly to the earth, unwilling to come out of his dark strongholds, hiding even his servants in shadows. The attack on Tilion caused the Valar to fortify their own land with high mountain walls called the Pelori, with towers, sentinels, and a host to watch the pass; and with the Enchanted Isles with their network of shadows and bewilderment. Thus, as Mandos, foretold, was Valinor shut away from the Noldor, and only the one foretold and planned for could come: the mariner Earendil.