Himself is the Ruler of Devils, and his seat of power and prison is a black iron coffin lashed with forty chains. He is pure ego, doesn't operate by the rules of reality and thus he is souvereign from decay, death or time. According to some theories, Himself is not overly concerned with staging his escape, as he bides his time until someone will free him - eventually.
The Heretic's Court is a council of 13 ebon devils that watch him to make sure he does not get out of his prison. The Heretic's Court takes its role very seriously. All major criminal activity through Devil syndicates in Throne requires his approval though, so they still let him hold court, they respect him (only) because of his enormous power. Himself has the important distinction of being named 'Himself', in a True Name kind of sense.
Himself, of course, considers his name to be MYSELF (inflected also I, ME and MY).
Allegedly, Himself was once summoned like all other devils, as a pale devil. Since then, he has gone a long way. However, the origin of his current power is unclear as it was also said that he freed himself from the Void.
Yabalchoath got approval from Himself and the Heretic's Council when she approached them for her first venture to the Treasure Fortress of Yre.. However, the Priests of the Count and the Heretic's court conspired and caused the downfall of Yabalchoaths reign, afterwards.
Allison and Cio had to travel to the White-Eyed Woman and Heretic's Council to ask for his approval about devils breaking into Yre again. Himself considered this his business, as Allison sought to use devils in the break-in. Himself gave approval for this adventure as part of a wager: If Allison were to be successful, she should "spare a thought" for Himself as a favor. If the enterprise were to be a failure, Himself promised that he would allow the Heretic's Council to kill Cio. This informal wager has been stated not to be an actual Devil's pact.