Sauron ends up emerging to fight Huan at one point; the landscape quickly starts shaking as Sauron flits between forms, favoring the shape of a massive wolf.

There doesn't seem to be a rear entrance. It's a very well designed fort.

What about going in from above?

She can't see any roof entrances (but she also can't see the roof), nor a single window that's larger than the size of an arrow slit, or really any way to easily climb the tower.

Guess she will be doing this the hard way.

She turns back to where Sauron is fighting Huan.

He's definitely tracking her location at least a little, but his attention is overall very consumed by the murder dog at his throat.

Then he will have a hard time reacting to the song of hers that swells over the battlefield, help and comfort to her allies that twists into pain and confusion to her enemies, and vice versa.

He spins up a counter-song - Huan is fundamentally a thing-that-rips-out-throats, not a thing-that-sings, so this part of his mind is less preoccupied.

Fear. Doubt. Can any really challenge him? Can she ever truly succeed, here? Her song is weak, he sings, and her voice will never shake the world.

Luthien doesn't fear, doesn't doubt. Her love is the ground on which she stands and nothing will dislodge her. From this rock she will move the world, and Sauron is but a pebble to be flicked aside.

Between them, she and Huan are forcing him on his back foot, and Huan's preventing him from lashing out physically at her. He attacks her with endings, with failing, with confusion and uncertainty, with his own past success, but - he's not landing on new cracks very easily. 

It helps that she's not completely improvising, she and Mygwainor have developed some approaches that are likely to work here...

He falters, losing ground - 

And Huan lunges and seizes his throat, pinning him. 

She closes to speaking distance.

"Here's how this will work. If you pass control of the tower to me, Huan will rip out your throat and your body will die quickly. If you don't, I kill you slow, and do the same again next time we meet."

He raises an eyebrow at her, apparently at worst mildly annoyed about the teeth pressing against his jugular. Then, tone almost flirty: "I see why she likes you."

And the control of the tower flips to her.

She stabs him in the gut and twists.

"I don't actually tell Huan what to do. Ask them nicely and maybe they'll make this faster."

She turns to the tower and begins deconstructing it.

The tower crumbles and drifts apart.

"Definitely see it!" he says, despite Huan's jaws clamping on his throat enough he shouldn't be able to talk. He's maybe cheating. "Do you have any sisters?"

She ignores him, and goes to the tower, where the prisoners would be.

He successfully annoys Huan into killing him before she gets very far (and before he can really hit on her again, at least).

Mygwainor is so imprisoned. Extremely. Very. There's bars and everything, and she's pretty sure 'being locked in a dungeon with Finrod' counts as torture (or did until he annoyed Sauron into drugging him).

She has a book set to the side and is looking up and over at Luthien, smiling. "My hero," she says.

"I've come to rescue you, my love."

"I've been pining away."

"Clearly." The cell bars bend out of the way. "You may be interested to know that your lieutenant attempted to hit on me, before Huan killed him."

She laughs and kisses her wife. "He does that! A few early loops I stuck him as Maedhros - who always gets captured by us - and he would not stop flirting."

"Sounds annoying."

"Actually convinced me to like him, eventually..." She shrugs. "I'd had nothing but pain and hatred and fear for him - or anyone other than your past self - back then, though, so it was - odd, the first time he made me laugh." Small kiss. "Though you'd beaten him to the honor a thousand times over."