Ancient Shrouded Armor

Ancient Shrouded Armor is a unique light armor set that appears in. It's an upgraded variation of the Shrouded Armor set but is visually the same.

Acquisition
The armor set can be obtained at the conclusion of the Dark Brotherhood side quest "Locate the Assassin of Old". The quest is given by Olava the Feeble and can only be accepted if the bonus requirement of Breaching Security has been met.

The armor itself can be found on the corpse of an assassin inside a secret room behind the throne in Hag's End. While Hag's End can be accessed before accepting the quest, the pull chain to open the secret door will not appear until Olava has been visited.

Smithing
All pieces of the Ancient Shrouded Armor set can be upgraded at a workbench with piece of Leather and the Arcane Blacksmith perk, however they do not benefit from any smithing perks.

This means the armor cannot be improved past flawless quality without boosting the Smithing skill over 100. This can be achieved by using enchanted items and/or blacksmithing potions to Fortify Smithing.

Patches
In older version of the game Olava's Token was required to get a reading from Olava to initiate her quest, however this is no longer neccesarry.

Bugs

 * The Cowl appears invisible on Khajiit (but removes part of the hair) and Argonians (removes hair and/or horns), however the Armor, Gloves and Boots are unchanged no matter the race. Using this Cowl on Khajiit and Argonians, you are able to wear most other helms at the same time providing both enchantments and bonuses. (Have tried with Nightingale hood, Shrouded Cowl Hood, Thieves Guild Hood, Guild Master's Hood, Dragonscale Helm, and Morokei)
 * The Ancient Cowl and the Worn Cowl can both be equipped at the same time along with other helms if you are playing a Khajiit.
 * It is possible to obtain multiple sets of this armor by looting the dead assassin then using the spell Dead Thrall on him and when you enter a new location his armor will respawn on him, then you can just kill him and repeat the process.
 * Using the Ritual Stone power in Hag's End can raise the assassin corpse. Killing it allows you to obtain the Ancient Shrouded Armor set without completing (or even starting) the Dark Brotherhood questline.