Seen as a reflection in a lake/pond in Krezk; he reached out to Ireena Kolyana and called her Tatyana.
Ireena remembered him as "Sergei" and he appeared to be related to Strahd von Zarovich (possibly his brother?).
He said "We were to be married long ago. Has your soul forgotten our love. Come to me Tatyana."
Strahd's face appeared in the clouds searching for something but faded away. "She is mine."