"Most of the overlords of the Age of Demons are truly bound, unable to affect the world in any meaningful way. A few have frayed their bonds, however, and have found ways to influence Eberron even while bound. In the modern age, Tiamat is stirring in the Pit of Five Sorrows, rousing dark emotions in the hearts of dragonkind. More important for Khorvaire, another overlord schemes: Seven centuries ago, he nearly escaped from his bonds. The paladin Tira Miron defeated him by becoming a vessel for the Silver Flame, but the overlord never truly returned to his slumber. For centuries he has lingered in the heart of the Silver Flame, whispering to the weak-willed and manipulating the path of the Prophecy to bring about an age of darkness. He draws strength from every feud and every act of betrayal, and the discord of the Last War increased his might significantly. Should he break free, chaos and despair will surely follow. He is Bel Shalor, the Shadow in the Flame. Some scholars claim that he is one and the same as the deity known as the Shadow, and that he taught the dragon Ouralonastrix the arts of magic at the dawn of time.
"While he is bound, Bel Shalor has little ability to directly influence the world. His power is one of insidious inspiration, of whispers in the dark. He has turned his prison against his captors, reaching through the bars or the Silver Flame to touch the minds of the faithful. Some followers of the Flame have been corrupted to actively worship BeI Shalor. His strength is his ability to trick good people into performing evil deeds; something he has accomplished all too often over the millennia."
--From the Eberron Campaign Guide, 4th Edition
Bel Shalor is an ancient demon lord from the Age of Demons and a member of the Lords of Dust . In ages past, Bel Shalor was imprisoned in the Silver Flame, an abstract object that is the direct opposite of all he is. Where the Flame represents loyalty, goodness, and order, Bel Shalor embodies treachery, evil, and chaos. His strength appears proportionate to (or at least dependent upon) the amount of strife and treason in the world.
Bel Shalor's power extends far beyond being able to physically thrash any being foolish enough to challenge him. If released, his malign influence would extend across Khorvaire in a matter of weeks. While under that influence, people pale and become sickly, even as they fight each other rather than stand united against him (however, certain heroes are powerful enough to be immune to this effect; Bel Shalor either dispatches minions to defeat them, or, if their threat is great enough, deals with them personally). Additionally, the shadows of all beings appear sharper, even in dim light. According to legend, these shadows betray their owners, whispering their secret plans to the Shadow in the Flame.
Bel Shalor's greatest servant is a Rakshasa known as Durastoran the Wyrmbreaker. Durastoren, said to be the greatest servant of the Lords of Dust, of the is an ancient being of great power and knowledge, who ultimately seeks Bel Shalor's release. While he waits, he plays deadly games with the draconic organization known as The Chamber.