The Impactors are Gransazers who migrated from Earth
It would explain why the armored forms of the Impactors resemble the Gransazers so much. Perhaps they left Earth to join Warp Monarch prior to their civilization's collapse. The "Planet Impactor" they come from could be a planet they colonized.The Chouseishin Series shares a universe with Seven Star Fighting God Guyferd
Beyond the fact that both are made by Toho, an artifact called the "Tablet of Daruga" which shares its name with Majin Daruga appeared in Guyferd. Considering the tablet was full of dark powers and a component for a doomsday device, it certainly fits with something Daruga would have had in his arsenal and could have originally belonged to him before winding up on Earth somehow.The Descal are descended from the same ancient civilization the Gransazers come from
Both the Descal and Gransazers come from ancient Earth civilizations and the Descal have a similar Elemental Powers quarter to the Gransazers (except with lightning instead of Earth, which makes sense since they live in outer space). It's possible the Biyodo aliens were part of the Warp Monarch force that came to Earth (which would certainly fit with their status as a prominent warrior race) and the Descal were actually made to flee by the Bosquito. Considering how muddled history became in Gransazer, it's possible the Descal came to blame the Biyodo for driving them off instead of the Bosquito.