- "Prince Aemon, the Dragonknight, may be the most famous Kingsguard who ever lived. How did he die? Defending Aegon the Unworthy from the brothers of a man who Aegon fed to his dogs. The man's crime? Sleeping with one of the many mistresses Aegon wasn't using. And the man was one of Aegon's own Kingsguard."
Terrence Toyne is mentioned within the entry of Aemon the Dragonknight in the The Book of Brothers. It is said that he was defeated by the Targaryen prince in the final joust in a tourney at Riverrun.
In the books
In the A Song of Ice and Fire novels, Ser Terrence Toyne was once found abed with Bethany Bracken, one of King Aegon the Unworthy's mistresses. Even though they proclaimed love, Aegon had them executed. Toyne was dismembered piece by piece, while the mistress was forced to watch before meeting her own death. Ser Terrence's brothers attempted to avenge him by killing King Aegon, but were stopped by Prince Aemon the Dragonknight who died defending him instead. They paid for their treason with their lives and in turn this event was key in the downfall of House Toyne, which in a few generations devolved into a family of rogues and robber knights, whereas others went into exile across the Narrow Sea. Simon Toyne, the leader of the Kingswood Brotherhood was the last of his line.