Catherine Arsaga is a renowned pokémon researcher 'retired' in Kethi City. She's mother to Nikki and Marcus Arsaga. Her husband, Taisto Arsaga, never returned from an explorative trip up Thorn. Whether that has any connection to Taqnateh has never been established (though it was speculated by Catherine in the Arsaga plotline, not that that's relevant for blank-slate canon). She's around forty years of age.
In Arsaga, Catherine Arsaga, unlike Marcus Arsaga, ends up exceptionally fond of Dakarai N'Sehla (platonically) after he helps save their life as the Arsaga questers encounter Ehqaj City's Tyranitar Trio - much to her son's chagrin. Her opinion changes as Devi Ravi reveals the degree to which Dakarai has been secretive, and she orders Devi and Marcus to stop harrassing him in the same breath as she tells Nikki to stop seeing him, imploring the group as a whole to focus on gathering facts rather than making assumptions either way.