At some point he purchased Beskha and when she was seven he forced her to fight in an arena, after growing bored of watching her kill animals he sent in other children instead and forced them to kill each other for nothing more than his own amusement. Ten years ago, Beskha bought her freedom, however, she still wishes for vengeance.
Beskha will leave Croft's planned route through Meereen. When Asher Forrester and Croft follow, they find her holding Dezhor at sword-point. When Croft objects to the plan, Asher can choose whether to allow Beskha to kill him which will improve her opinion of Asher but risk the wrath of Daenerys Targaryen who had ordered them not to kill any of the masters, he can follow Daenerys' orders and stop Beskha which greatly annoys her or Asher can just kill him himself much to the dismay of both Beskha and Croft.
In the books
While there is no equivalent character in the A Song of Ice and Fire novels, there is a mention that in some fighting pits on Astapor slave children are employed as entertainment. For example in Douquor's pit there is mention of a "folly" involving a bear and three small boys - One boy is to be rolled in honey, one in blood and one in rotting fish, and spectators can bet on which child will the bear devour first. There is also a mention of a nine year old girl fighting at Jothiel's Pit.