Huinesoron got it
 

NINIEL: She is made of three elements in disarray.
2. In confusion, praise a dwarf, for him.
3. Endless element in turmoil, inside a ruse. See him!
4. Adhesive, linger! Hear it for her.
5. An unsung cry returns for him.
6. Diminish an artificial sweetener for him (with slight adjustment).
7. A confused Rohirric warrior gains direction, for him.
8. Chaotically, a small herb reveals her.
9. He is made of a turbulence and a bird.

9 is the easiest.

NIPHREDIL for the password, perhaps?

Forget that.

9. STORMCROW?

Password: NICKNAMES.

Yes. Will add when I get home.

5. NOM.

Name given to Finrod Felagund by Beor and his followers.

MOAN backwards, with the A unsung.

NINIEL: She is made of three elements in disarray.
I: In confusion, praise a dwarf, for him.
C: Endless element in turmoil, inside a ruse. See him!
K: Adhesive, linger! Hear it for her.
NOM: An unsung cry returns for him.
A: Diminish an artificial sweetener for him (with slight adjustment).
M: A confused Rohirric warrior gains direction, for him.
E: Chaotically, a small herb reveals her.
STORMCROW: He is made of a turbulence and a bird.

K could be KEMENTARI, which is nearly 'cement, tarry'.

hS

NINIEL: She is made of three elements in disarray.
I: In confusion, praise a dwarf, for him.
C: Endless element in turmoil, inside a ruse. See him!
KEMENTARI: Adhesive, linger! Hear it for her.
NOM: An unsung cry returns for him.
A: Diminish an artificial sweetener for him (with slight adjustment).
M: A confused Rohirric warrior gains direction, for him.
E: Chaotically, a small herb reveals her.
STORMCROW: He is made of a turbulence and a bird.

Not seeing an element yet, but I've remembered a nickname beginning with C: CAMLOST.

Hang on, though. We need a ruse as well. I could not find a suitable word. Unless it's CHEAT?

I might be INGLORION.

Ori? Oin? Groin? Gloin? Nori? Loni?

The only praise element I can see is GLORY without the Y, which leaves the little-known dwarf Noin. :D

CELEBRINDAL.

A ruse could be a BLIND.

CELEAR is left ....

Hint: You used this exact name in one of your recent passwords.

IORHAEL.

And I thought of Iorhael yesterday but completely forgot to post it.

Ori + (sounds like hail).

NINIEL: She is made of three elements in disarray.
IORHAEL: In confusion, praise a dwarf, for him.
C: Endless element in turmoil, inside a ruse. See him!
KEMENTARI: Adhesive, linger! Hear it for her.
NOM: An unsung cry returns for him.
A: Diminish a dessert ingredient for him (with slight adjustment).
M: A confused Rohirric warrior gains direction, for him.
E: Chaotically, a small herb reveals her.
STORMCROW: He is made of a turbulence and a bird.

Changed the A clue slightly to make it more accurate.

I think Equal is a sweetener in America.

If you lose the Q and shuffle it, you can get AULE, but as far as I know that isn't a nickname.

Hang on, though ... ARAW is. Is there a sweetener containing those 4 letters?

I edited that clue.

Aranel / Caramel?

Nope.

Agarwaen / Aspartame.

NINIEL: She is made of three elements in disarray.
IORHAEL: In confusion, praise a dwarf, for him.
C: Endless element in turmoil, inside a ruse. See him!
KEMENTARI: Adhesive, linger! Hear it for her.
NOM: An unsung cry returns for him.
AGARWAEN: Diminish a dessert ingredient for him (with slight adjustment).
M: A confused Rohirric warrior gains direction, for him.
E: Chaotically, a small herb reveals her.
STORMCROW: He is made of a turbulence and a bird.

C - CELEBORN has CON.

His original name WAS Teleporno, I believe.

The ruse is CON, but it's not Celeborn. The clue says that it's an endless element inside a ruse, which doesn't fit with Celeborn.

CUTHALION.

'Uthali' is an anagram of 'thaliu[m]'.

(Only got this because it's pretty much the only nickname in the set of CO??????N + C??????ON.)

hS

NINIEL: She is made of three elements in disarray.
IORHAEL: In confusion, praise a dwarf, for him.
CUTHALION: Endless element in turmoil, inside a ruse. See him!
KEMENTARI: Adhesive, linger! Hear it for her.
NOM: An unsung cry returns for him.
AGARWAEN: Diminish a dessert ingredient for him (with slight adjustment).
M: A confused Rohirric warrior gains direction, for him.
E: Chaotically, a small herb reveals her.
STORMCROW: He is made of a turbulence and a bird.

The last two are Valarin nicknames.

Hama + L = Mahal.

NINIEL: She is made of three elements in disarray.
IORHAEL: In confusion, praise a dwarf, for him.
CUTHALION: Endless element in turmoil, inside a ruse. See him!
KEMENTARI: Adhesive, linger! Hear it for her.
NOM: An unsung cry returns for him.
AGARWAEN: Diminish a dessert ingredient for him (with slight adjustment).
MAHAL: A confused Rohirric warrior gains direction, for him.
E: Chaotically, a small herb reveals her.
STORMCROW: He is made of a turbulence and a bird.

The nearest thing to a herb I could find was Eierplant for ELENTARI.

You got the right person, but look at her other nicknames.

Well, first of all I tried to find some kind of herb with 'berry' at the end for Elbereth, but without success.

NINIEL: She is made of three elements in disarray.
IORHAEL: In confusion, praise a dwarf, for him.
CUTHALION: Endless element in turmoil, inside a ruse. See him!
KEMENTARI: Adhesive, linger! Hear it for her.
NOM: An unsung cry returns for him.
AGARWAEN: Diminish a dessert ingredient for him (with slight adjustment).
MAHAL: A confused Rohirric warrior gains direction, for him.
ELBERETH: Chaotically, a small herb reveals her.
STORMCROW: He is made of a turbulence and a bird.

Also, do I have to say 'it is your turn' in order for people to realize this?!

If you think I'm going to sacrifice quality time with my dad on holiday to post the password a couple of hours earlier, or ignore the fact that he is now old enough to need some assistance in order to post straight away that I will post it as soon as I am able, you have another think coming.

As it happens, I worked out another one on the coach.

Hope you like it.

1. A French circle spins for him.
2. Burrowing mammals' concerts and insects' pity combine for them.
3. Festival articles for her.
4. A claw and a nun's cap were sedentary, before they spun around for him.
5. Shop changes tune, unwilling, for him.
6. Confused Field Marshal at start of Merseyside peninsula transforms for him.
7. Wander unmethodically for him.
8. A unit of measure, a vowel shift ... shuffle and see her.

1. Elrond (from Le Rond)

Nope.

The only words I could find were ROND and CERCLE.

You are turning the wrong bit into French.

P.S. Clues 6 and 7 are probably the easiest ones.