Grizzaka is the Earth Overlord and holder of the Grizzly Bear Animal Spirit, master of the power of Zocato that makes him the strongest of the Overlords. He also wears gloves that can sprout claws from the back of his hands.
After Dai Shi's defeat by the Jungle Master Red Ranger, Carnisoar and Jellica send Camille to revive Grizzaka to increase Dai Shi's power. However, being short-tempered, Grizzaka blames Dai Shi for losing the Beast War centuries ago and hates humans even more. Once revived by Camille, whom he attacked until she pleas him to come with her, Grizzaka overthrows Dai Shi because of his current status as a human and becomes the new leader with Carnisoar and Jellica switching loyalties out of fear of their wellbeing. His current goal is to gather the Crystal Eyes that will release the Phantom Beasts from their prison. After Jellica captured Jarrod, he ended up in a fight with Jarrod where during the fight, he mentioned that the Control Dagger Dominic has is needed to get into the Rhino Nexus. Grizzaka defeated Jarrod again while using the Zocato Power.
After Jarrod/Dai Shi escaped, he took Carnisoar and Jellica to the Rhino Nexus. Upon running afoul of the Power Rangers, Grizzaka managed to defeat the Jungle Master Megazord (even when it had Bat Power and later Shark Power). Grizzaka ended up occupied by the Sand Snakes that guarded the Rhino Nexus.
When Jarrod/Dai Shi returned to the castle, Grizzaka was defeated by Jarrod/Dai Shi's Zocato. Grizzaka left to gather fear in Ocean Bluff. Grizzaka then fought the Power Rangers while Casey tried to reclaim the Crystal Eyes from Camille and Jarrod/Dai Shi. Grizzaka was overwhelming them until Casey arrived. Casey used a combination of the Claw Booster and Dominic's Rhino Morpher to fight Grizzaka. Grizzaka was taken down by the Claw Cannon, Wolf Morpher and Rhino Blade. Grizzaka grows and the Rangers form the Jungle Master Megazord and the Wolf Pride Megazord. Grizzaka overwhelmed the Megazords until Dominic brings out the Rhino Pride Megazord. Grizzaka then fights the Rhino Pride Megazord and are taken down. He was then destroyed by a new formation involving the Steel Rhino Megazord, the Wolf Zord, and the Jungle Master Zords. Grizzaka was revived by Dai Shi for the final Beast War, but was destroyed again by the Jungle Fury Power Rangers and the Pai Zhua Masters.