Cernunnos is the first Folklore of the game and is the guardian to the Faery Realm. It is met in Chapter 1 of the storyline and requires a successful Timed Absorption to beat.
Walkthrough
When the tentacles begin sucking things up, use Bargest. The tentacle will suck him up, though it may take a few tries for Bargest to be in range. When Bargest gets stuck inside a tentacle, use Ogma to cut him out. Stick to Cernuos's sides to avoid being attacked. Repeat this until both tentacles are gone.
Once the tentacles are gone, Cernunnos will collapse into the ground. A flower will bloom on his back. Use Boobrie to attack it. The flower will spit seeds at you. use Killmoulis to block them. Use Ogma to cut any spikes that get in the way.
Attack the head of Cernunnos using Bargest until it collapses.
When the flower appears, attack it with Hinky-Punk. Defend with Killmoulis when it shoots seeds at you.Origin
It is based on the god Cernnunos from Irish myth. Cernnunos was an antlered god who represented the wilderness and its ferocity. Cernnunos in the game keeps the antlers and appears to be constructed from swamp matter and leaves.