Pazuzu

Pazuzu is one of the oldest demon lords in the Abyss, as he is one of the few surviving obyrith demon lords. While the Queen of Chaos was in power, Pazuzu remained an independent demon lord. This saved him during the tanar'ri revolt against the Queen of Chaos, as he was not affiliated to her. Following the tanar'ri conquest of the Abyss, Pazuzu was quick to adapt with the change. This has manifested in several ways: While most obyriths, having been conceived out of the Abyss's chaotic will itself, have characteristically bizarre physical appearances, Pazuzu appears as human-like as any tanar'ri. Pazuzu's abilities have changed as well: He can now summon tanar'ri, and the obyrith form of madnessability has changed as well. While most obyriths' visages are so chaotic that merely looking at one causes insanity, Pazuzu's newfound appearance has changed his form of madness into an "Aura of Servile Avians." This ability causes all evil flying creatures to feel an affinity towards Pazuzu, making it hard for them to bring themselves to attack the demon lord.

Goals
Pazuzu is viewed by the denizens of the Abyss with resentment and grudging respect. Unlike most demon lords, he is not interested in conquest of the Abyss. His main concern is winning followers on the Prime Material Plane by tempting or deceiving those of good alignment. He aids any good creature who summons him, in order to tempt him or her to evil. In the Monster Manual II, he is said to be on good terms with daemons (now known as yugoloths) and the dukes of Hell.

Relationships
In the "Demonomicon of Iggwilv" and Fiendish Codex I: Hordes of the Abyss, Graz'zt is listed as Pazuzu's most notable enemy. Graz'zt alone takes umbrage at Pazuzu's claim to dominion over the skies of the Abyss, though the Prince of Tyrants has never taken action against him beyond the occasional insult. Pazuzu is also opposed by the obscure demon lord Lamashtu, "She Who Erases", the Demon Queen of Monstrous Births and Deformity. She was a former consort of Pazuzu, and is the only being who knows Pazuzu's true name. She betrayed him, and in response he ate her eyes and imprisoned the Queen of Monstrous Births on Torremor, where she has remained impaled on a spire there ever since.

The 4th edition Demonomicon establishes that Pazuzu's most powerful and secret ally is Asmodeus. In the new default setting, Pazuzu aided Asmodeus in obtaining a sliver of the shard of pure evil that festers at the bottom of the Abyss. The sliver became Asmodeus's signature Ruby Rod, which the angel used to slay the god he served. Those few who know of the ancient deal believe that the King of Hell has yet to repay Pazuzu for this "favor".

Cults of Pazuzu
Pazuzu is the lord of all evil flying creatures and all birds and avian creatures. His worshippers rarely emerge in societies; usually he is worshipped by lone individuals. His primary worshippers include Kenku, harpies, gargoyles, manticores, wyverns, and sometimes evil fey or dragons or aaracokra. His temples lie in areas unreachable by those incapable of flight: in wildernesses, atop cliffs, or on mountain peaks. He was also worshipped by the Aearee, one of the Creator Races, of the Aearee-Quor Empire beginning in the year of -30400 DR

Full article on the cults of Pazuzu