The monsters used by the Crisis Empire are referred to as Strange Demon Soldiers. There are four branches each lead by an Officer. While Granzyrus appears in Earth, Maribaron uses her power to revive members of the each other armies into the Spirit World Kaijin Army, being greyed versions of themselves before being destroyed by BioRider.
The Sunriser is RX's transformation belt that is actually the King Stone. The King Stone was split in half and is able to communicate to him telepathically and use sunlight to power RX up. That factor places RX at a disadvantage while in an area that has no sunlight. The Sunriser also allows for Form Change, changing its design to suit the form.