Katrina was Morgan's first and most intense love, a servant girl in 14th century Nuremberg. She flirted with Morgan -- a monk -- and was as shocked as he was when she won his heart. Their brief love affair seemed doomed when she contracted the Plague, but Morgan's secret deal with the Devil provided the miracle that gave them 10 years together. The events of those years will be gradually revealed over the course of the series, leading to a deeper understanding of Morgan's origins.
Ona was 7 months pregnant when she returned in Season 3 as part of her recurring role in the series.