Gothmog vs. Sauron

[Pitchwife]

Originally Posted by Galadriel55

They can exist in Arda without a body, though. An elve's fea would not be able to do that. When it is separated fro the body, it goes straight to Mandos.

Not necessarily - it's not like Mandos has some great spiritual vacuum-cleaner that sucks all bodiless fëar into his halls willy-nilly. He summons them, but while most elvish fëar will obey the summons, they all have the freedom to refuse it, and some do, roaming Middle-earth in their disembodied state. It can be speculated that at least some (maybe most?) of the spirits Sauron conjured and misused in his necromany were such 'houseless' elvish fëar (probably of Avarin origin).

Originally Posted by Galadriel55

When Isildur chopped off the Ring, he lost almost all of his power and was not able to take a physical form again (it is possible that he would regain that power if he got the Ring back, but I'm not sure about this).

That's one of the many popular misconceptions spread by the movies. According to the book, Sauron had regained his physical form at the time of the War of the Ring. Gollum met him in the flesh and told Frodo and Sam that 'He has only nine fingers on his black hand'.