Nightingale Blade

The Nightingale Blade is a unique One-Handed sword found in The Elder Scrolls V: Skyrim. It once belonged to the Nightingale and Thieves Guild leader Gallus Desidenius.

Acquisition
It is given to the Dragonborn as a reward by Karliah upon completion the Thieve's Guild quest, Hard Answers.

Smithing
The Nightingale Blade can be upgraded with an Ebony Ingot and the Arcane Blacksmith perk, however it does not benefit from any smithing perks.

Levels
The damage, weight and value as well as the magnitude of the enchantment is based on the level the Dragonborn obtains the weapon. The best possible version is available at level 46.

Trivia
It has a unique enchantment called Nightingale's Talon
 * PC Users can type  into the console and let the game's level system randomly choose which version of the weapon to add.

Bugs

 * Returning to the Dwemer museum before meeting Karliah at the Ragged Flaggon will re-activate the quest to obtain Calcemo's research and thus you can receive another Nightingale Blade. (You may be required to do this if Karliah does not move from Winterhold after you receive the first blade.)
 * The highest level version of the Nightingale Blade seems bugged and does not show up in the improvement menu after interacting with a Grindstone. All other versions do show up and can be improved.
 * To avoid the bug above, you need to edit the improvement recipe of the blade using the Creation Kit : open, in Items / Constructible Object, TemperWeaponNightingaleBlade05 and set Created Object to NightingaleBlade05 (instead of NightingaleBlade04, a false value) ; save your change in a plugin (a .esp file) and active this one when you start the game.

Appearances
Соловьиный Клинок