Pa Bil Sag, or Pabilsag, was the tutelary god for the cities of Larak and (alongside his wife) Isin in Mesopotamian mythology. He was regarded as a son of Enlil, who was also the father of Nergal. Early on, he was conflated with yet another of Enlil's sons, the popular god Ninurta, which makes it difficult to identify his original attributes. It's possible he was a god of healing, of law, a netherworld deity, or perhaps a divine huntsman. He was also a war god known under the title of "Warrior of Enlil," likely borrowed from Ninurta.
The most significant text related to Pabilsag is Pabilsag's journey to Nibru, in which he honored Enlil and presented him with many gifts. This myth calls him "the wild bull with multicolored legs." It seems that a partially preserved fragment additionally describes his marriage to Nininsinna, a healer goddess. Together they had a son, Damu, who was himself a healing god; some researchers consider him to be analogous to Dumuzid.
Originally, Pabilsag was depicted in the garb of an official, but later art sometimes shows him as a centaur-like figure with the tail of a scorpion. In this form, he was associated with the constellation Sagittarius. He wasn't an influence on the Greek centaurs.
In the Enuma Elish, when Tiamat waged war on the gods, scorpion men, distinct from the god Pabilsag, were among the creatures fighting for her. Like her other servants, they were vanquished by Marduk.
The hero Gilgamesh encountered scorpion men during his search for immortality. A pair of them, seemingly husband and wife, guarded the gates located at Mount Mashu, where the sun was said to rise, which Gilgamesh had to pass to reach his destination. While described as fearsome (their "glance is death"), they are not malevolent in this myth, unlike their Enuma Elish equivalents, and let Gilgamesh continue his journey.
"Origin: Iraq. A half-scorpion, half-human therianthrope. He is the Babylonian guardian of the gate connecting the human and demon worlds. Gilgamesh descended through this gate on his search for immortality. The Centaur of Greek lore is said to be modeled on Pabilsag."
—Shin Megami Tensei A-Mode DDS dictionary
Shin Megami Tensei IMAGINE
"A half-man, half-beast monster from Mesopotamian mythology. He is also called Ninurta and revered as a god of war. Pa Bil Sag is both highly intelligent and tremendously strong. He resembles a cross between a man and a scorpion in appearance, and is said to guard the gate between the human world and the demon world. When the hero Gilgamesh descended into the demon world in search of immortality, he came to this gate guarded by Pa Bil Sag. Pa Bil Sag aimed his bow at Gilgamesh, and was such a terrible sight to behold that even Gilgamesh, slayer of countless monsters, recoiled in fear. Later, when Marduk achieved godhood and started a war, Pa Bil Sag fought alongside Tiamat, the goddess who gave birth to the gods, but was defeated. Pa Bil Sag is thought to be the model for the half-man, half-horse centaurs of Greek mythology, and for the modern constellation Sagittarius."
—Shin Megami Tensei IMAGINE compendium
Pabilsag can be contracted within the Shinagawa Catacombs of the Templar Knights.
Shin Megami Tensei IV
Pabilsag is the messenger of the god Enlil and the one who Flynn must deliver Heaven's Tablet to in the New Game Plus Challenge Quest, Retrieve the Tablet. He resides in a building found in Ginza - Shopping District in both the first playthrough and NG+. He states that the Tablet of Heaven's Will holds the destinies of the gods, which is why they cannot touch it themselves and must rely on Flynn to retrieve it. After obtaining the tablet he confesses that he had always viewed humans as weak, but realizes that might be an error considering he obtained such an important item. He leaves to take Heaven's Tablet to his father Enlil.
Shin Megami Tensei IV Apocalypse
Pabilsag can teach Nanashi the Tathlum Shot, Toxic Sting and Rapid Needle skills through his Demon Whisper. He benefits from learning gun and ailment skills.
Persona Q: Shadow of the Labyrinth
"A guardian of the gates of paradise, this beast with a human head and a scorpion body appears in Mesopotamian Lore."
—Persona Q: Shadow of the Labyrinth compendium
Devil Survivor 2
"A scorpion-man of Babylonian lore. He is worshipped as a beautiful holy beast, full of intelligence. He guards the rising and setting sun from darkness at Mt. Mashu."