Gandalf, Moria, and Arrest

[Belegorn]

Originally Posted by Moonraker

I actually think this was just an inconsistency with the true nature of Gandalf as a Maiar from the Hobbit to the Lord of the Rings. I don't believe anything but a Maiar could have killed Gandalf the Grey, and a powerful one at that.

I have to disagree. Sauron, while bearing the One Ring was defeated by Gil-galad and Elendil the Tall. An Elf and a Dúnadan. Hardly Maiar themselves.

Originally Posted by Silmarillion; Of the Rings of Power and the Third Age

Sauron himself came forth: and he wrestled with Gil-galad and Elendil, and they both were slain, and the sword of Elendil broke under him as he fell. But Sauron also was thrown down

Originally Posted by FotR; The Council of Elrond

I beheld the last combat on the slopes of Orodruin, where Gil-galad and Elendil fell, and Narsil broke beneath him; but Sauron himself was overthrown, and Isildur cut the Ring from his hand

Originally Posted by Letter #131

Gilgalad and Elendil are slain in the act of slaying Sauron.

These are some of the references to Sauron dueling with an Elf and Dúnadan and both parties killing each other, like what happened with Gandalf and the Balrog. I'd say it's possible that Gandalf could be killed with weapons these guys possessed.