Seylan's first acting role was in 2014 when she responded to a facebook post and was cast as the Older Witch in Macbeth (StudioCanal, dir J. Kurzel). She has appeared in numerous productions since, most recently Doctor Who (BBC) as Tecteun and Host (Shudder, dir R. Savage) the ground-breaking zoom horror filmed remotely during Covid-19 lockdown, where she plays the medium in an online séance.