According to Ozpin, the Nuckelavee Grimm was created by the God of Darkness. Centuries later, the creature attacked the town of Kuroyuri, destroying it beyond repair and killing most of the citizens living there; including Lie Ren's parents.
In "Remembrance", Team RNJR comes across the ruined town of Shion, which has been attacked and destroyed by the Nuckelavee Grimm. Ren and Nora notice the creature's footprint in the dirt, but decide to say nothing.
In "Two Steps Forward, Two Steps Back", Ruby and Jaune take Qrow down the path to the ruined town of Kuroyuri, unaware of the Nuckelavee Grimm's footprint beneath them.
In "Kuroyuri", Ren and Nora discover a cave where the Nuckelavee Grimm has been living and leaving behind tokens of its conquests. Upon looking out the other side, they see the trees ruffling as the Nuckelavee Grimm roars and makes its way toward Kuroyuri.
In "Taking Control", the Nuckelavee Grimm arrives at Kuroyuri, roaring as it spots Team RNJR.
In "No Safe Haven", the Nuckelavee Grimm battles Team RNJR, overpowering them with ease. Ren attempts to attack it and gets pinned by the Grimm, forcing Nora to save him but getting beaten and depleted of Aura in the process. Ren breaks free and charges the creature again in a blind rage, but is also defeated and depleted of Aura. Ren soon comes to his senses after some words from Nora and together Team RNJR devises a plan to defeat the Grimm; pinning the humanoid portions arms to the ground while Nora kills the equine portion with Magnhild. Ren then severs the humanoid portions limbs before decapitating it, killing the Grimm and avenging his parents as well as everyone the creature has slain.
Powers and Abilities
The Nuckelavee Grimm is quite powerful compared to the rest of its kind, being responsible for the destruction of both Kuroyuri and Shion. Its humanoid portion has extendable arms and a discomforting screech that briefly stuns its enemies while the equine portion attacks with its legs and hooves. When it gets angered, the Nuckelavee Grimm increases its strength, giving it longer spikes and causing the humanoid portions mouth to open completely.
- The Grimm appears to be based on the Nuckelavee, a creature from Orcadian mythology with origins from both Norse & Scottish mythology. The Nuckelavee was commonly blamed for disease and destruction of crops.