I think the "thank you" element is either "ta" or "Tar" (conversational word for "thank you"). That's as far as I got last night - this part of the clue was the one that at first had me the most bewildered! (and I may still be wrong, of course).
Also, I didn't know what an epesse was and had to look it up - so I learned something new as well! (Thanks Mith).
I reckoned it might be one of the Numerorean kings/queens with the "Tar" prefix left off. But I didn't have time to look through them all last night. (I guessed it was another "work backwards" clue - that like with minim/Mim you had to remove some letters to get to the answer, rather than add them).
I even tried removing "ta" from the word "star" - and mingling it with "land" or "land in" in disarray (jumbled up). And I nearly, but not quite, got
Sirandilas - now, I don't know if that's even a Tolkienian name. I just remember someone once using it as a user name on a Tolkien discussion board.
Nerdanel has "land" in it, but also has several other letters that don't fit. Ditto
Thranduil.
So I reckon it might be the name of a country, jumbled up, plus maybe s and r. Hmmmmm ....
I wasn't including "gains" in the anagram, because I thought it just indicated to
add land or land in (jumbled up) to sr (star minus ta) ....
Or it could start with EL for star - but that still wouldn't take care of the "thank you" absence thing.