In Greek Mythology, Horkos is a personification of a curse that will befall anyone who swears a false oath or breaks an oath they had taken. He was also the god of death, karma and justice. His Roman counterpart is Orcus.
He is the son of the goddess Eris, and brother of Ponos, Limos, Algea, the Hysminai, the Makhai, the Phonoi, the Androktasiai, the Neikea, the Pseudologoi, the Amphilogiai, Dysnomia, Ate and Lethe. Hesiod states that the Erinyes assisted at the birth of Horkos, and that the fifth of the month was especially dangerous as being the day on which he was born. However, there is no fixed day on which the god’s punishment falls on the wicked.
During medieval times, he was depicted with the head of a pig who ravaged corpses, most likely because sacrifices to him used pigs. Horkos was thought to be the king of the Orcs.
"A god of death originating in Greek lore. During medieval times, he was depicted as a demon with the head of a pig who ravaged corpses, most likely because sacrifices to him used pigs. Horkos was thought to be the king of the Orcs."
—Shin Megami Tensei: Strange Journey compendium
Horkos appears as the strongest demon in Sector Carina. He calls himself "a great prince of Hel" at the first encounter, and repeatedly screams "BUONO!" He fuses himself with the damaged remnants of the Elve, and with its energy shields becomes able to shrug off all damage, leaving him unscathed. Mastema offered to create the Shibboleth to help them, which will damage his ability to devour the Elve's energy, from two demons (any Megami demon along with any Wilder demon), but states it would need further augmentation to pierce the Elve's shields.
The protagonist creates the Horkos Buster, a plasma cannon tailored to flush Horkos out of the Elve's systems, leaving him vulnerable to physical damage. Infuriated from the loss of the Elve, he later attacks the Red Sprite with the full intention of absorbing it as he had done to the Elve. He was repelled by the Red Sprite's energy shields and forced to evacuate via Carina's Sanctum System to his lair. Pursued to the depths of Carina, Horkos is slain by the hand of the protagonist, cursing humans for their limitless hunger, which exceeded even his.
Horkos is revived in Sector Fornax by Mother Tiamat; even after taking his true form Orcus, he still lost. At his death, the Red Sprite's crew recovered his rare forma and Sector Carina's Rosetta.
During the battle against him, Horkos uses Grocery Run to summon a Katakirauwa. After the Katakirauwa sustains enough damage, he will use Binge Eating to kill it before the party can, while healing HP proportional to his ally's HP at the time of use. Horkos also inherits the status ailments of the allies he swallows. Whenever Horkos chooses to, he can use Taking a Bite, an attack similar to Life Drain. The Katakirauwa is also susceptible to all ailments, and if it is eaten while charmed or muted, Horkos will also become charmed/muted, allowing for several rounds during which he will attack himself/be left unable to use his skills for the entire battle. If he is muted, and buffs at the party and debuffs on Horkos are at +4/-4, Horkos is rendered completely incapable of attacking, at which point the protagonist can auto-battle him with no struggle whatsoever. He is a special fusion that's unlocked after his defeat.
"A god of death originating in Greco-Roman lore. In those days, he was depicted as a demon with the head of a pig, most likely because sacrifices to him commonly used pigs."
—Shin Megami Tensei IV Apocalypse compendium
Horkos can be found on the second version of the Fairy Forest. He teach Nanashi the Critical Wave and Megaton Press skills through his Demon Whisper. He benefits from learning Physical attack skills.
Shin Megami Tensei: Liberation Dx2[]
"A demon in Greek mythology, and king of the vile Orcs. In the middle ages pigs were often used in animal sacrifice, which may be why he is often depicted with a hogs' head."