Baalzebul is one of the middle crop of infernal dukes. Back in the day, Baalzebul was known as the archon Triel. Triel was a very selfish perfectionist who kept wanting more and more out of his existence, which eventually caused his fall from grace. After being welcomed into hell, Triel rose through the ranks and attained the title of the Lord of the Flies, supposedly because his webs of intrigue were so tight that not even a fly could slip past him, though many pointed to the archduke's multifaceted, fly-like eyes.
Baalzebul eventually made his way to the rank of archduke and partook in the rebellion against Asmodeus. He was defeated but, though clever maneuvering, managed to hold onto his lordship anyway. But Asmodeus got the last laugh by giving such Belial two curses- first, he would spend a year in the form of that hideous slug-like monster over on the right every time he lied to another devil... including all the lies he told before that curse was placed, meaning he had to go through a several-thousand-year span of being in this state and only recently was able to return to his true form again. But while in this form, Baalzebul is easily the most grotesque and disgusting of all the archdukes. Presumably it is his vanity that prevents such a clever bastard as him from exploiting the loophole in this curse, a loophole which surely would be obvious to any devil worth their salt: the curse is completely useless as a lie detector if he lies to someone while already in slug form.
Secondly, no deal Baazebul makes would ever turn out well for the other party. Even if Baalzebul genuinely wishes to make a mutually beneficial bargain, events will conspire to make whoever he dealt with regret it. This doesn't affect his dealings with mortals much since they don't tend to know about hellish politics and thus have no idea this curse is a thing, but it has neatly snipped most of his political power in the bud, as now every devil knows better than to accept any offer he makes.
To this day Baalzebul craves the downfall of Asmodeus as revenge for this humiliation. Thus far, he's had little success with this plan, but the Lord of the Flies has established a notable cultist presence on the Material Plane through a combination of lies, charm and promises of power. Aside from Asmodeus, Baalzebul despises Mephistopheles, who was one of his opponents during the rebellion in Hell. He counts Belial as an ally, but his daughter and co-ruler's relationship with Glasya and her growing power base makes this alliance at best unreliable.
Baalzebul's cults consist of individuals who, like him, suffered a fall from grace, and wish to regain their former glory. To this end, he grants the Path of Baalzebul, which allows a cultist to choose one ally to give Disadvantage to all ability checks and attack rolls for a turn, while the cultist themselves gets Advantage on the same, allowing them to make themselves look good to those who don't know about the diabolic source of their sudden fortune. The Cult of Baalzebul's signature spells are Minor Illusion, Disguise Self, Phantasmal Force, and Major Image.
|The Archdukes of Hell|
|Avernus||Bel or Zariel|