[T 1] Commentators have noted that since the Maiar are immortals but can choose to become fully incarnate in men's bodies on Middle-earth, they can be killed; Tolkien did not explain what happened to them then.
According to the Valaquenta, many Maiar associated themselves with a particular Vala; for example, Salmar created for his lord Ulmo great conches who produce the music of the sea known as Ulumúri,[T 2] while Curumo, who came to be known in Middle-earth as Saruman, was with Aulë the smith.
These include the Chiefs of the Maiar, Eönwë the Herald of Manwë, King of the Valar, and Ilmarë the Handmaiden of Varda, Lady of the Stars;[T 4] Ossë and Uinen, spirits who rule the seas and act under the Lord of Waters Ulmo;[T 4] Arien, guide of the sun and a spirit of fire uncorrupted by Melkor; Olórin, the wisest Maia, and Tilion, guide of the moon and the servant of the Huntsman of the Valar, Oromë.
[T 9] The Maia Melian went to Middle-earth prior to the First Age, where she later fell in love with the Elven-king Elu Thingol, King Greymantle, and with him ruled the kingdom of Doriath.
[6] The theologian Ralph C. Wood describes the Valar and Maiar as being what Christians "would call angels", intermediaries between the creator, named as Eru Ilúvatar in The Silmarillion, and the created cosmos.
He notes that Sauron's inability ever to take bodily form again after his defeat could be the result of having given his power to the One Ring, but that the fate of slain Maiar remains unclear.
He states that they have "perpetual importance in the cosmic order", noting the statement in The Silmarillion that their joy "is as an air that they breathe in all their days, whose thought flows in a tide untroubled from the heights to the deeps.