Things that do not have room for Amshalan:
Doors.
Hallways.
Most ordinary rooms, at least with furniture in them.
The mirror-mouth of this snake monster that is eating her Chosen.
" - I mean, I am not expecting you to be dead set against it on my account, there's a lot more at stake here."
"I know, I get that, but this whole thing sounds like a nasty mess and you might be a useful indicator of how flexible he is and how damaged he is by the Angband and the body swap. So you're an available bridge to not burn."
Nod. "Thank you. - still much rather be out of here before he comes. If you think you have any ideas -"
"I can try some things. I can generally oppose most magic worked here in Imladris, I'd just want to make sure I understood what I was doing."
"I don't think I can be of much help, even if there's a creative Mindspeech or Thoughtsensing application I'm not going to figure it out on my own any time soon."
"It seems pretty unlikely but if it were a contingency against betraying him or something you wouldn't know and you might still want it out."
So he gets to work on trying to undo the foreign magic that has Maedhros's soul pinned into such a bizarre configuration. It is frustrating work. In places it feels like trying to peel back an oath, which can't be done; in other places it feels like it might tear away a bit more cleanly, but that doesn't make it straightforward to actually do. Maedhros's can't let him work for very long without breaks to go wander Imladris, even though he's clearly trying very hard to get this done with as soon as possible.
He has more luck while Maedhros is sleeping. He finds his way around the mind, finds some of the more loosely-attached foreign magic, studies it, gets a very detailed feel for it, reaches for it with Vilya. Tells it that this is Imladris, where the universe works the way he wants it to, and he wants Maedhros to be healed, to be free, more than anything -
" - I can sing for it but not quite yet, I think, I want it as a diagnostic first. Does this feel like the time you threw one off -"
"I'm not going to be able to get all of them that way. Some of it's - more like an oath, I can't budge that. But some of it should be possible to get off, I think. If we do one per night then in a few weeks -"
"No. I might cause you brain damage. If you lie back down and accurately report your symptoms I will consider whether we can do them more frequently."
"You can shop around for other healers in possession of Rings of Power who have fewer concerns about this, then. I will of course have someone carry you anywhere you want to go."
"I know. Lie down, drink some water, accurately report your symptoms, and we'll see how quickly this can safely be done."
"Okay. ...I apologize. I appreciate that you are inventing something new and not known to be possible on the spot for me."
"It very clearly ought to be possible, the Rings do interactions with other magics and they almost always win. I'm actually kind of puzzled about the part I don't see an angle to shake loose of your head. Do you know if it might be some other kind of magic?"