Ysalus was a planet involved in the Last Great Time War.
Romana oversaw the CIA’s intervention in Ysalus’ civil war, and arranged the planet’s preservation in a time freeze after the intervention failed, due to coming into conflict with a rival War Council Intervention, and instead escalating the war. (AUDIO: Partisans)
She was later informed by General Dalia that the freeze had been breached and Scythes were scavenging the planet. Together they worked with a native, Knyla Shen, to organise an evacuation of Yslaus, with Romana sending Eris back in time one year to meet Kynla, and enable her to make contact with Gallifrey in the first place. The War Council erased Ysalus from time, with Kynla being too late to reach the CIA’s TARDISes. After learning Rassilon has arranged this whole Incident as a example, Romana discovered that Eris had helped Kynla send a signal across time calling for a resistance against the Time War. She arranged the signal’s preservation and helped Eris escape Gallifrey. (AUDIO: Collateral)