Celina Sinden: Celina Sinden. Actress: The Outpost. Celina Sinden is an English actress hailing from London. After spending some years in London's fashion industry Celina went on to study at the Guildhall School of Music and Drama, completing a three year acting degree. She then starred as regular 'Greer' in television series 'Reign' on the CW which ran for four seasons.