"From this day forth, the killing of a cleric of Asha'dar shall be considered a legal act."
To put it bluntly, Asha'dar is not a popular deity in Outland. To be more concise, Asha'dar is hated and despised by those who know of him, and his worship is expressly forbidden. In fact, in the year 507 AS, the Dominion Council went so far as to legalize the killing of a cleric of Asha'dar.
Currently, there are no known clerics or followers of Asha'dar in Outland.