I really like this, and I love that even just a sprig of Athelas is helping them endure the Ice.

This is wonderful - I love that you wrote it as a letter! That really plays into the whole "explorer's notebook" element of the challenge. Also the fact that he's writing the letter to Maedhros is heart-wrenching in exactly the right way. 

I like the idea that they found kingsfoil and it gave them a little hope, even if even the hope is painful. (And I suppose Maitimo will need so much of it later on, after the rescue from Thangorodrim, if it is to be had...)

The idea that Fingon is counting days from the Doom makes me sad but makes total sense.

This is a really interesting idea. And the PS were heart-breaking! Now I can't help but wonder what other letters Fingon may have written during the trek across the ice!

Oof, there was a lot packed into this letter, wasn't there!

Their suffering on the ice, not harped on but none the less present.  And this line>> But then, no one here is in their right minds – I least of all. << oof!

Then the flower, of course - the titular element - athelas!  I love how the smell lingers and lifts them up!  Beautiful fic! <3