Myrkul

Lore
Myrkul, also known as the Old Lord Skull, was one of the Dead Three and the Neutral Evil god of the dead, as opposed to the god of murder, which was the province of Bhaal and the god of tyranny, Bane.

Long ago Myrkul was a powerful adventuring necromancer in his mortal years, traveling with Bane and Bhaal, dedicated each to a quest to attain divinity for themselves. They traveled to the citadel of Jergal who, luckily for them was tiring of his existence as lord of the end of everything. Breaking off his skeletal knucklebones after an argument over which of the three would rule over the other two, they were each thrown by the mortals to determine which of Jergal's portfolios they would receive. The end result was Myrkul gaining the portfolio of the Dead. Jergal served Myrkul as an aide for a time until Myrkul had settled into his new role.

During the Time of Troubles, roughly at the time Bhaal died, his avatar was slain by Cyric who inherited his portfolio as god of the dead thereafter.

The whole story can be found in-game in the book History of the Dead Three.