Dark Sister

From A Wiki of Ice and Fire

Dark Sister is a famous sword of Valyrian Steel.
The sword was in the posession of Aegon I sister and wife Visenya Targaryen. It was probably passed through the Targaryen line by inheretence and became later in the posession of Bloodraven. Unknown is if Bloodraven was allowed to take the sword with him when he was banished to the Wall. Since then nothing is known of its whereabouts.