Sheepland is Numenor, isn't it? Erendis and Ancalime don't want to leave their sheep, IIRC.

Nope.

Erm ... Durin III?

So we can see it on the new page.

Maybe ALDARION for number 10. (The clue, not Downing Street).

5. ELROS, equating Numenor with Atlantis?

TAR-MIRIEL: The one who should have been 4th.
2. A headwear, a grip and an element reveal a king's best friend.
3. By another name, she is named after a jewel (estrangement).
4. Islandic river? It's the biggest.
5. The first ruler of Atlantis.
CELEBRIMBOR: Fist of silver. The only decent fellow among his immediate kin.
7. A Vala and Turin meet, initially, in this place.
NIMRODEL: A girl who shares a name with a stream.
DURIN III: Third of this name. His people are devoted to Mahal.
ALDARION: An eager adventurer. Loved the sea.
11. Lady of Adamant. (Call).
12. Sheep land.

I was going for Anardil, but since they're the same person, it works.

3. ERENDIS? (Elestirne)

5. ELROS?

I don't know if 'sheep land' needs to be a whole country, but EMERIE is the sheep district of Numenor.

TAR-MIRIEL: The one who should have been 4th.
2. A headwear, a grip and an element reveal a king's best friend.
ERENDIS: By another name, she is named after a jewel (estrangement).
4. Islandic river? It's the biggest.
ELROS: The first ruler of Atlantis.
CELEBRIMBOR: Fist of silver. The only decent fellow among his immediate kin.
7. A Vala and Turin meet, initially, in this place.
NIMRODEL: A girl who shares a name with a stream.
DURIN III: Third of this name. His people are devoted to Mahal.
ALDARION: An eager adventurer. Loved the sea.
11. Lady of Adamant. (Call).
EMERIE: Sheep land.

Password: The Second Age.

4. Siril.

11. Galadriel, because of the Ring of Adamant?

2. Hat-hold-ir, friend of Tar-Meneldur.

Would the last one be Ossiriand?

TAR-MIRIEL: The one who should have been 4th.
HATHOLDIR: A headwear, a grip and an element reveal a king's best friend.
ERENDIS: By another name, she is named after a jewel (estrangement).
SIRIL: Islandic river? It's the biggest.
ELROS: The first ruler of Atlantis.
CELEBRIMBOR: Fist of silver. The only decent fellow among his immediate kin.
O: A Vala and Turin meet, initially, in this place.
NIMRODEL: A girl who shares a name with a stream.
DURIN III: Third of this name. His people are devoted to Mahal.
ALDARION: An eager adventurer. Loved the sea.
GALADRIEL: Lady of Adamant. (Call).
EMERIE: Sheep land.

No. My bad, that one is cryptic too.

Orome + t(urin) ?

TAR-MIRIEL: The one who should have been 4th.
HATHOLDIR: A headwear, a grip and an element reveal a king's best friend.
ERENDIS: By another name, she is named after a jewel (estrangement).
SIRIL: Islandic river? It's the biggest.
ELROS: The first ruler of Atlantis.
CELEBRIMBOR: Fist of silver. The only decent fellow among his immediate kin.
OROMET: A Vala and Turin meet, initially, in this place.
NIMRODEL: A girl who shares a name with a stream.
DURIN III: Third of this name. His people are devoted to Mahal.
ALDARION: An eager adventurer. Loved the sea.
GALADRIEL: Lady of Adamant. (Call).
EMERIE: Sheep land.

And the new one is yours.

Here we go, then:

1. It drags the bearer earthwards.
2. Zero edge to this hang-out! But it’s colossal.
3. Within a vow are mingled a note, two ways and two eyes, we hear? There!
4. A Fallohide shows it to a Stoor.
5. Here! Lisp an orcish preposition, and add a legal property right!
6. May they redirect a mumak!

3. Osgiliath (Oath + Two I's + S + L + G)

Precisely!
 

1. It drags the bearer earthwards.
2. Zero edge to this hang-out! But it’s colossal.
OSGILIATH: Within a vow are mingled a note, two ways and two eyes, we hear? There!
4. A Fallohide shows it to a Stoor.
5. Here! Lisp an orcish preposition, and add a legal property right!
6. May they redirect a mumak!

The first one isn't The One Ring is it?

It is, but can you give it a descriptive name? (Descriptive in a way that goes with how the clue refers to it).

Burden for 1?

That's the one!
 

BURDEN: It drags the bearer earthwards.
2. Zero edge to this hang-out! But it’s colossal.
OSGILIATH: Within a vow are mingled a note, two ways and two eyes, we hear? There!
4. A Fallohide shows it to a Stoor.
5. Here! Lisp an orcish preposition, and add a legal property right!
6. May they redirect a mumak!

Regarding 5, there are no Orcish prepositions.

There is one. I've used it here before, but long, long ago.

Is it Ithilien (Ithi+lien)?

2. Oliphaunt, from O (zero) + lip (sort of edge) + haunt (hang-out)

And thus Book VI for the password?

Yes. One can extrapolate that 'ishi' means 'in' from 'agh burzum-ishi krimpatul.'

Nearly ... nearly ...

(Yes to OLIPHAUNT).

BURDEN: It drags the bearer earthwards.
OLIPHAUNT: Zero edge to this hang-out! But it’s colossal.
OSGILIATH: Within a vow are mingled a note, two ways and two eyes, we hear? There!
4. A Fallohide shows it to a Stoor.
5. Here! Lisp an orcish preposition, and add a legal property right!
6. May they redirect a mumak!

I think Tolkien used 'lip' in that sense: 'the lip of the dell,' or something.

You forgot 'Ithilien'.

Book IV for the password?

BURDEN: It drags the bearer earthwards.
OLIPHAUNT: Zero edge to this hang-out! But it’s colossal.
OSGILIATH: Within a vow are mingled a note, two ways and two eyes, we hear? There!
K: A Fallohide shows it to a Stoor.

ITHILIEN: Here! Lisp an orcish preposition, and add a legal property right!
V: May they redirect a mumak!

Yes. I think that's what Galadriel meant, too. BOOK VI was my last one. ;)

Lol. No Oliphaunts in Book VI, except the ones Sam regrets not seeing. :D

V for Valar then! See Mablung / Damrod's (forget which one actually said it) prayer-like exclamation when they guard Frodo and Sam.

Easy to make typos with Roman numerals. ;)

'Mumak! Mumak! May the Valar turn him aside!'

(I guess lady oliphaunts didn't go to war?) :D Or maybe he was referring to the rider.

BURDEN: It drags the bearer earthwards.
OLIPHAUNT: Zero edge to this hang-out! But it’s colossal.
OSGILIATH: Within a vow are mingled a note, two ways and two eyes, we hear? There!
K: A Fallohide shows it to a Stoor.

ITHILIEN: Here! Lisp an orcish preposition, and add a legal property right!
VALAR: May they redirect a mumak!

So which of us gets the next turn? :p

You can have it, you got the right book. ;)

One clue to go first, though! ;)

Knife for the last one? (Is Frodo a Fallohide?)

Ooohhh, that's a good one!

However, right Fallohide, right Stoor, wrong thing.

(Frodo has Fallohide blood, yes. Hence his physical appearance and adventurous nature. And skill with languages and speech. He would presumably also have some Harfoot traits from his Baggins father, though, like Bilbo had).