Reapers
From Super-wiki
Reapers appear in 1.12 Faith (episode) and 2.01 In My Time Of Dying (episode).
The Reaper in the episode Faith is more commonly known as a psychopomp, a spirit or entity whose responsibility it is to escort newly-deceased souls to the afterlife.
The character of Tessa in 2.01 In My Time Of Dying (episode) is arguably a reference to Neil Gaiman's "Death" character, as seen in his Sandman series of graphic novels.