The Dark One has many names The Corrupter, The Horned God, and Shaitan to name a few.
The Dark One appears as an appealing form to those he/she appears to. The Dark One then slowly seduces and feeds them council and slowly but surely corrupts them.
The Dark One is an insidious threat to everyone and everything.
Patron to multiple individuals and factions. The most notorious is the Minos Brotherhood.
The Dark One's goal is total dominion of the Mortal Realm.
For followers of the One God, The Corrupter is the single most dangerous threat to their belief and way of life.