|Book(s)||A Dance with Dragons (mentioned)|
The Dance of the Dragons
He was killed by Princess Rhaenyra Targaryen's dragon Syrax during the civil war known as the Dance of the Dragons. He tried to kill the dragon by sneaking up behind his shield so the dragon would see only its reflection, as Serwyn of the Mirror Shield famously did to the dragon Urrax.
Grand Maester Munkun stated in his book The Dance of the Dragons, A True Telling that it was the dragon Vhagar who Ser Byron tried to kill. However this is unlikely since Vhagar was ridden by Prince Aemond Targaryen, the brother of King Aegon II and House Swann supported Aegon II. Ser Byron's squire, who saw him die, wrote his daughter that Syrax killed Ser Byron.