Ysabel Andronicus is the Battle Matron of the Arena, and she trains the Grand Champion. She does not seem interested in speaking with low-ranking members of the Arena, and if the Hero tries to talk to her shortly after joining the Arena, she will only tell them to leave her alone.
If they ask about the Battle Matron Owyn mentions, in passing, that she is 'dear' to him, but he does not elaborate. After becoming Grand Champion, they will find that Owyn asked Ysabel to marry him; she rejected him.
Ysabel arranges the final person on person fight in the Arena, between the Grey Prince and the Hero. Upon winning, they can receive either the Light Raiment of Valor or the Heavy Raiment of Valor from her.
Ysabel arranges creature fights for them after they becomes the Grand Champion. If they talk to Ysabel before becoming Grand Champion, she will say she doesn't have the time to talk and would rather have them talk to Owyn.
"And who in Shinji's name might you be? Look, if you're a spectator, go upstairs and talk to the Gatekeeper. This ain't no damned peep show."