Rawkus is a space golem who is an ally to the Battle Force 5. Known as the "Eternal Equalizer", his mission is to maintain balance in the Multiverse by making certain no faction dominates the others. As such, he cannot determine the outcome of a battle.
Ever since Rawkus first came to life, he has been wandering the Multiverse for eons performing his mission. At one point nearing the end of the war between the Red and Blue Sentients, he met Master Takeyasu and saved Sage's life by bringing down his rock scythe on Krytus, sending him to his Re-Spawn Chamber.
Rawkus would run into Krytus again many years later when he, Kyburi, and Kytren steal his Power Core Stone. He also crossed paths with the Battle Force 5 when Sage picked up Krytus's telepathic link. Low on energy, he steals Stanford's Sentient Chip and takes off after the Red Sentients. Zoom Takazumi follows him into the Red Sentient homeworld.
Despite Rawkus's insistence, Zoom helps him out, saying a wise quote his former teacher said to him. Rawkus begins to trust Zoom as they await a rescue by the rest of the Battle Force 5. He nearly powers down due to a loss of charge in the Sentient Chip he took, but upon being freed, Zoom reinserted his Power Core Stone. He took down the remaining two of the Red Sentient 5 before leading the way out of the planet. He rides away, vowing to meet them again, but implying he may not be on their side when they meet again one day. Their second meeting would come sooner rather than later, in the episode, "The Shadow Zone"
In Unite and Strike, Rawkus informs Krytus of the Battle Force 5 trying to stop him, but this turned out to be a set up for alliance with the Blue Sentients. Also, a similar character attacked the Battle Force 5, but was yellow and had a chopper bike.
Being an Earth based being, he has control over rock using a scythe. In his chest is his Power Core Stone, he needs this to stay alive (he has been shown to use a Sentient Chip in an emergency). Without it, he's rendered inanimate for a millennium. He is also shown to have a slight degree of control of time, but it can only be used in an emergency.
The Grindstone is a motorcycle ridden by Rawkus. This gigantic motorcycle is made from stone with a molten core that spins, creating lava-blasting exhaust plumes.