From A Wiki of Ice and Fire
|Book||Fire & Blood (mentioned)|
In 73 AC, Denys took part in a tourney held by his father to celebrate the birth of another son. Denys was defeated by a mystery knight called the Silver Fool, who was later revealed to be Prince Baelon Targaryen.
- Fire & Blood, The Long Reign - Jaehaerys and Alysanne: Policy, Progeny, and Pain.