Bar'Traxia Bargruush

One of the great demon lords that ruled the abyssal planes ages ago.  Before the time of Aer'Chabadzael and Anaxis the lower planes were ordered and boundaries set.  Much like the gods in the Veiled Sanctum, the demon lords that ruled the hell dimensions wielded their powers in a similar fashion.  
Bar'Traxia was one of these, perhaps the most charismatic and intelligent.  When the hell dimensions were broken and thrown into chaos the great demon lords fought to regain control.  Anaxis actually killed a few of these as well at the same time he was attacking the gods.  Before that though, Aer'Chabadzael had attempted a similar coup of the hell dimensions and found himself in a war with Bar'Traxia.  The conflict grew and the enmity between the two became unbearable as things spiralled out of control.  These two major events took centuries and the battles fought created the chaos the demon dimensions now survive in.  Many of the Demon Lords were destroyed or scattered to other planes of existence.  
Bar'Traxia survived the wars and did his part to trap Aer'Chabadzael in his dark domain and prison.  The wars cost him a physical form and his home but he still survives.  Now he empowers others to help him regain a body but he will never stop hating the Dark One and he will do anything to keep him imprisoned or destroy him. 
He is the patron of many warlocks but his favorite right now is a young Tiefling woman named Ariantha...
[DM Note: It is possible that Ariantha is Bar'Traxia's daughter.  Bar'Traxia often walks the world of Tanaheim using a human or elven host.  Possessing the body and seducing women for his own ends.  Whether he is or not the father he will consider Ariantha his daughter.  It is why he chose her to empower and he watches her often.]