Canon Background
https://awoiaf.westeros.org/index.php/Leo_Blackbar

In-Campaign
Ser Leo was surprised when Ser Shaymus returned to Bandallon a week after his departure, and even more surprised to see the weary knight had brought with him Ser Darron and a contingent from House Jasper. Ser Leo was open handed with his visitors and explained he had no personal grievance with Darron. Rather, he had supported The Blackshield in taking Darron’s sword because Darron was alleged to have taken the jewels of House Mullendore. Those jewels were the last remnant of the Mullendores’ days as petty kings. He did also share that Blackshield had left a gambling debt of 2ss with the household guard. Ser Carsen freely offered to pay the debt. After witnessing the chivalry Ser Leo informed that Blackshield had departed heading east days earlier in the company of Ser Bert Webber and Ser Gwayne Flowers… but that he knew no more. The Jaspers thanked him and quickly set out again.