From A Wiki of Ice and Fire
Dark Sister is a famous Valyrian steel longsword, one of two ancestral swords of House Targaryen (the other being Blackfyre). Dark Sister was wielded by at least one woman during its history and may have been forged for a woman warrior originally as its slender blade is designed for a woman's hand.  The sword is last known to have been wielded by Brynden Rivers.
The sword was in the possession of the Targaryens since before the War of Conquest and probably passed down the line by inheritance. It was usually given to younger sons. It was known to be wielded by:
- Visenya Targaryen - Aegon's elder sister-and-wife
- Prince Daemon Targaryen 
- Prince Aemon Targaryen, the Dragonknight
- Lord Brynden Rivers, Bloodraven 
It is unknown whether Bloodraven was allowed to take the sword with him when he was sent to the Night’s Watch. The sword's current whereabouts have as yet not been revealed.
Quotes about Dark Sister
|“||She has a thirst for blood.||”|