Cerberus appears as a creature made up of three different spheres linked together by chains. The ones in front have spiked collars and legs. One head is red and has an attribute of Fire. The second head is blue and has an attribute of Ice. The third head, which connects the other two heads together, is yellow and sports an attribute of Thunder. Like the other two heads, the third head has a spiked collar and a ring in its left ear.
While only a Second Level Nightmaren, Cerberus is openly feared by allies and enemies alike (including NiGHTS and Reala) seemingly functioning as a weapon of last resort (Wizeman notes that "they have... quite a temper"). Cerberus is also referred to as "they" or "them" because of the same personalities from each head.
Cerberus will relentlessly pursue NiGHTS throughout the fight, charging at her/him for a chance to take a bite out of the jester. For this situation, the Rocket Persona is the best choice until the Cerberus pauses briefly. NiGHTS must yank on the third orb to knock the heads of Fire and Ice together, stunning them for a bit. The light on the orb in the center changes from blue to yellow to red, indicating how much damage has been done. In the second fight, however, approaching the third orb isn't as easy, for the Thunder head will lash out when NiGHTS gets close enough, dealing five seconds' worth of damage if it bites her/him. Once the Orbs of Ice and Fire have collided three times, the Orb of Thunder detonates, destroying the hellhound.
Cerberus' area appears in Delight City, disguised as a dog's kennel. Once the player enters the area, they find themselves in a null and endless void. The Cerberus lives in a spherical cage with big black crows flying around in it.
- Cerberus is not one dog with three heads, but two dog-like Nightmarens connected by a chain, which is actually the third dog.
- The part of the chain you push to make the heads clash is actually the third head. It isn't known until the second battle.
- The name of Cerberus' theme is "Clashing Cerberus".
- In Greek and Roman mythology, Cerberus is a three-headed hound who guards the gates of the Underworld. It also said that the hellhound is Hades' lapdog.
- According to Reala, Cerberus is referred to as "That mad old dog that will devour anything in sight" meaning that the dog like nightmaren viciously attacks anyone whether it's a Visitor, Nightopian or Nightmaren.