Spectral sequence of SN 2020qlb. The dark blue SN 2020qlb spectra were smoothed using a Savitzky-Golay low pass filter. A lighter shade of blue is used for un-smoothed data and measurement errors. Spectra from a well studied SLSN-I (SN 2015bn) are shown in gray for comparison. P-Cygni profile minima used for velocity estimations are marked in dark red. Narrow host galaxy emission lines ([O III], Hα and [O II]) used for redshift estimation are indicated with green, red and blue vertical dashed lines. Blended Fe II absorption features, as well as [Mg I] and [Ca II] emission features are noted in black. Nebular phase [O I] and [O II] broad emission lines are noted in green.