Gillestes was a Yevnon who studied at the Gallifreyan Academy where Braxiatel's behavioural projection flagged her as subversive.
Antimon manipulated Gillestes into becoming a Free Time agent, but she did not fully understand the group's aims. She downloaded Braxiatel's Matrix codes for Antimon and was stopped from contaminating the water supply with the Dogma Virus by Andred, who subdued her and handed her over to Wynter. She was able to offer very little information. (AUDIO: Pandora)
Darkel later spoke to Gillestes and learnt from her about the Dogma Virus. (AUDIO: Insurgency)