BLIZZARD: Plosive meets slithery thing (we hear) on Caradhras.
RINGBEARING: ABBA song swallows little Beatrice. It’s exhausting!
ORCS: Oo, they’re awful!
NEEKERBREEKERS: Cousins of Vogons? They torment with onomatopoeia!
WATCHER IN THE WATER: Submerged stalker, or just a wet TV addict?
EMYN MUIL: Lovable rugby player loses surname and liquid, but gains an equine hybrid here, we hear!
AMON HEN: Grumble about chicken? Here?
THIRST: ‘Lotsss of thisss in Mordor, my Preciouss!’ (he gasped).
HUNGER: Do this only for a taste of justice or a world of truth. (The twin of the last clue).
AMON SUL: Nice place? No, a slum. Messed up.
NAZGUL: Breathing apparatus swallows map-book, in confusion. (They’re so bad at finding people, you’d think they had, too).
HORROR OF SHELOB: Terror of Cirith Ungol.
AMON AMARTH: Morning marathon around (or rather up) here – and the final one.
R: To hear these might well dement. Perhaps they were played to Frodo in Cirith Ungol?
TREE-ROOTS: Much harder than feather-beds!
HOMELESSNESS: Hateful road brings epiphany of danger – and this.
ARAGORN'S SINGING: Beren and Luthien, brought to the camp-fire by this.
DEAD MARSHES: Inanimate bogs.
PASSWORD: BRONWE ATHAN HARTHAD ('Endurance Beyond Hope' - a name given to Frodo, post-quest, by Gandalf, in an early draft of 'The Lord Of The Rings').
THEME: Things or experiences endured by the Ringbearer (with number 14 as a trick question/odd one out).
Amon Sul indeed, also known as Weathertop, where Frodo received the Morgul-knife wound.
You remember me saying I didn't want to make it too maudlin? Well, I had to find four answers beginning with A, and couldn't bring myself to use 'Amputation.' So I chose three hills to get Amon ----- three times, (each connected with a wounding and/or a difficult experience), and decided to cast wicked aspersions upon Strider's vocal talents.
Also, the T could have been torment of some kind, but I preferred to choose the more light-hearted 'Tree-roots.'
LAST REMAINING CLUE: Don't worry about 'dement.' It's only there because 'might well dement' is a phrase I absorbed years ago from a war poem. I think it referred to the sound of something.* The things in question here are well-known in Tolkien fandom, but were NOT written by Tolkien himself!
* I've just checked, and it's from 'Six Young Men' by Ted Hughes, one of my O Level poems. I had thought it referred to horrible war sounds that might dement, but I must have conflated that with 'The shrill demented choirs of wailing shells' from 'Anthem For Doomed Youth' by Wilfred Owen. The actual line is 'To regard this photograph might well dement,' - it *does* concern World War One, but it's about a photograph of six young men before they went to war, and how every single one of them died shortly afterwards - in the Great War. The comment means that just *looking* at this photograph could send you mad, (the subsequent slaughter being so senseless and so tragic). (None of which, however, will help you solve the last clue!)