Selection of resonance lines in the spectrum of RW Cep. Rows from top to bottom: Ba II λ6141.71, Ca I λ6572.78, K I doublet λλ7698.96, 7664.91, and Na I D₂ λ5895.92. Odd-numbered panels show the line profiles in August 1999 (blue, ELODIE), July 2003 (orange, ELODIE), and December 2006 (green, ESPaDOnS) and even- numbered panels show the profiles during the Great Dimming minimum in January 2023 (purple, FIES) and 9 months later in September 2023 (red, FIES). Additionally, a telluric standard spectrum from the same January 2023 night has been included (light grey) to display the locations of blending telluric lines, especially in K I. For the K I only ESPaDOnS and FIES spectra are displayed due to the limited spectral range of ELODIE. Grey vertical lines trace the location of the emission peak at –56 km s⁻¹ and also at ±40 km s⁻¹ from it to help guide the eye.