Mask

Mask is a loner god, most often associated with thieves or those of otherwise ill-repute. Known for his constant scheming, cool head, and oft reserved biting comment he has recently lost a significant portion of his power (the intrigue portfolio) to Cyric. This has of course lead to two things, an enduring hatred of Cyric and the Lord of Shadows leading himself to be more direct than his prior elaborate plots.

Relationships
Simply put, Mask is a loner. However, he has had both frequent (in the past) and infrequent (in the present) alliances with Bane. If nothing else, the two's sizable hatred of Cyric gives them a common ground in addition to their history of working together. Mask is also at direct odds with Waukeen (the goddess of merchants, and honest trade), of course, all guardians of light, knowledge, and duty are opposed to him, as well as Selûne, whose light tends to reveal his own faithful whilst they work.

Kezef the Chaos Hound
In the years following the Time of Troubles, Mask released the powerful hound Kezef to try and kill Cyric, but the hound turned instead on the Lord of Shadows and did not stop chasing Mask until it had bitten off one of the god's limbs (which Mask was seemingly now too weak to heal) and Mask acquired the powerful weapon Houndsbane to defend himself.

Dogma
"All that occurs within shadows is in the purview of Mask. Ownership is nine-tenths of what is right, and ownership is defined as possession. The world belongs to the quick, the smooth-tongued, and the light-fingered. Stealth and wariness are virtues, as are glibness and the skill to say one thing and mean another, twisting a situation to your advantage. Wealth rightfully belongs to those who can acquire it. Strive to end each day with more wealth than you began it, but steal what is most vital, not everything at hand. Honesty is for fools, but apparent honesty is valuable. Make every truth seem plausible, and never lie when you can tell the truth but leave a mistaken impression. Subtlety is everything. Manipulation is better than force, especially when you can make people think they have done something on their own initiative. Never do the obvious except to conceal something else. Trust in the shadows, for the bright way makes you an easy target."

Godsbane
During the Time of Troubles Mask took shape of a powerful blade called Godsbane. He would eventually come to be wielded by the then-mortal Cyric during the Time of Troubles. Cyric acquired the sword by murdering a halfling named Sneakabout, who in turn killed the former wielder of the sword.