Cernunnos was a horned fertility god in Celtic mythology. Cernunnos was also identified as the Horned God in Neopaganism, where he represents the seasons in a year in an annual cycle of life, death and rebirth.
The demon behind the Wicker Hordes in the Challenge Quest, "Serial Kidnapping - Arson." He appears after the last Horde is defeated and states that the more people who die in his name, the more his status and power rises, with it not mattering how they die, as long as they do in his name. He attacks Flynn in order to grow stronger by killing him. He reveals in the battle that his goal is to return to being the God of Fertility and Harvest like in ancient times and bring back the ancient gods. Cernunnos is surprised at his defeat, as the Wicker Man sacrifices should have increased his power and finds Flynn to be one crazy human, but tells him he still hasn't given up and that he'll resurrect other ancient gods to aid him next time.
Cernunnos appears in a later Challenge Quest called "Multi-Demon Fusion," where he has taken control of several hunters and is using them to fuse more ancient gods like himself. After Baphomet loses, he appears and is angry that Flynn is once again interfering, but warns him that it's too late to stop him as he tells Baphomet to fuse and regain his godhood as Pales. He reveals his goal of restoring the old gods to amass a army to crush God himself and that mankind shall be their sacrifice for this goal. He fights Flynn alongside Pales, disappearing after losing.
"A beast god of Celtic lore, worshipped by Druids. His name means "horned one." He has deer antlers and is usually pictured with horned snakes. He is the god of the dead, hunting, fertility, and vegetation."
—Shin Megami Tensei IV Apocalypse compendium
Cernunnos can teach Nanashi the Cough, Death's Door, Megidola and Mamudoon skills through his Demon Whisper. He benefits from learning ailment, Darkness and Electricity skills.
Known as Kanos, he confronts Akira at Rem blvd. in hopes of taking the bounty on his head and getting the opportunity to rule the human world of Rem as the reward. To stop Kranos, Akira fights and defeats him. Upon his defeat he reveals that Lena has been executed by the Imperius and they can do nothing to stop them from taking over the three worlds or creating the Time Rifts.