A Blade Between Oaths by R.M.

Skyrim bleeds in silence. While Jarls posture and empires crumble, something ancient stirs beneath the snow, unseen, unheard, unchallenged. The Thieves Guild rises once more, not as mere pickpockets or rogues, but as phantoms dancing in Nocturnal's shadow.

At the heart of it, honour still stands. Barely. The Companions, bound by oath and tradition, cling to order in a world that no longer listens. But in chaos, only shadows thrive, and she would make sure of it. She is known only by the trail she leaves behind. A whisper cloaked in black, unspoken. A myth walking the halls of Jorrvaskr. A Nightingale without a past, without a name.
She comes as a warning for them all.
If the Companions would not act for Skyrim, someone else would.

Among them, Vilkas walks the old path, sword in hand, duty burning in his chest. But honour is brittle when met with the unknown. What use is tradition when the Nightingale moves faster than a wolf can catch her scent?
He will die before he gives up on uncovering the truth. And she will only haunt him for the sake of it.

Here lands the realisation that some enemies can't be slain.
Some bonds were never meant to form.
And some stories were never meant to be told in daylight.