Blackfyre, one of two ancestral Valyrian steel longswords of House Targaryen, brought to Westeros by Aegon I. Blackfyre was passed from Targaryen king to king, until Aegon the Unworthy bestowed it on his bastard son Daemon instead of his legitimate son, Daeron, After the Daemon's death, his half brother Bittersteel took Blackfyre with him in exile to the Free Cities, where he and Daemon's surviving kin founded the mercenary force, the Golden Company. The sword's current whereabouts are…
Eustace Osgrey by Mike Miller. “Aye, we were pardoned. So long as we bent the knee and gave him a hostage to ensure our future loyalty, Daeron forgave the traitors and the rebels. I bought my head back with my daughter’s life....A king’s mercy is a poisoned gift. Daeron Targaryen left me life, but took my pride and dreams and honor. I should have... died beside my sons and my sweet king. That would have been a death worthy of a chequy lion.... Daeron’s mercy made me smaller.”
Daeron I Targaryen, The Young Dragon, was the eldest son of Aegon III and the eighth Targaryen king to sit the Iron Throne from 157-161 AC. He ascended to the throne at the age of fourteen and is famous for conquering Dorne, which he wrote about in his Conquest of Dorne.
Daenys Targaryen, also known as Daenys the Dreamer, was the daughter of Lord Aenar Targaryen. She was born in Valyria and had prophetic dreams (like Prince Daeron Targaryen and Daemon II Blackfyre). She saw the Doom of Valyria and warned her father, who relocated his family to Dragonstone, despite the jokes from the other lords. That's why the Targaryens are the only family of dragonlords that survived the cataclysm.