Dark Sun: The Scorched World of Athas
Devils are agents of evil where they forever bicker and plot in the deep reaches of the Astral Sea. Devious and nefarious, devils find no scheme too convoluted and with the absence of the divine, they turn their attentions to the mortal worlds.
Because of their connection to the Astral Sea, devils are rarely encountered on Athas, as travel to and from that place is extremely difficult.
Withering devils harvest souls by sapping the vitality out of all that they meet. By tempting or tricking mortals into apathy and depression, withering devils cause famine, plague and strife.