Pirok is a Toa of Fire.
Approximately 400 years before the events of the RPG, Pirok was friends with a Le-Matoran. However, this Matoran disappeared, around the same time another Matoran named Proditor was banished from Le-Koro, supposedly for killing another Matoran. Pirok suspected the Matoran killed was his friend, and spent many centuries trying to track Proditor down and avenge his friend.
He eventually found Proditor at the Kini-Nui. After punching him, and knocking him unconscious, Pirok himself fell unconscious. He awoke soon enough, and travelled down a tunnel after several other Toa, including Merror, LoJak, and JL. Soon, they were attacked by Rahkshi, and Pirok caved in the tunnel while under the power of Kurahk.
When they climbed up, they met a Toa named Vanboi, and travelled to Le-Koro.