Ragorus is a Toa of Magnetism who was once a Toa Hagah (his team was protecting Antroz). When the Hagah team guarding Teridax betrayed the Brotherhood, Ragorus's team was destroyed by Antroz. Ragorus was frozen in a block of ice until he was discovered in the ruins of the giant Mata Nui robot by Toa Tahu and his team.
That's a pretty cool story. By the way, does that 'H' mean anything imparticular?