|Book(s)||Fire & Blood (mentioned)|
Durign Aegon's Conquest the lords of the Three Sisters declared their independence from King Ronnel Arryn, and installed lady Marla Sunderland, Steffon's older sister, as their Queen. However, when the conquest was done and House Arryn swore their alligence to House Targaryen, King Aegon I sent an army under the command of Ser Warrick Manderly and Queen Visenya Targaryen, which was tasked with putting the rebelion down. However, the lords of the Sisters were not willing to face queen's dragon Vhagar, and deposed Queen Marla in favor of Steffon. Lord Steffon renewed his fealty to House Arryn and bent the knee to Queen Visenya. He had to give over two of his sons as a hostages, one was send to White Harbor, and the second to Eyrie. .
- Fire & Blood, Reign of the Dragon - The Wars of King Aegon I.