Before the first visit of Arceus other than strange sightings people believed like how he shaped Regirock, Regice, and Registeel. Regigas shaped the planet they built it temples and monuments, even giving him sacred places such as The Twist Mountain and The Island Cave. The ancient texts say "At snow's pointed finger is where Regigas shall slumber ,and when awoken shall help us or, strong wielders of his Elemental grandchildren watched by the three Titans of ice, steel, and rock shall be able to obtain the wisdom of the Grandmaster Titan, Regigigas". Meaning that only a strong trainer can enter his temple and by figuring out the riddle in this ancient text the people of the modern day era discovered the temple of Snowpoint Hill. In other words even though today it was disproven that does not mean that this wasn't a very important point in our history. It also says that all legendary Pokemon in Sinnoh were created by Regigias as they thought Arceus, Dialga, Palkia, and Giritina were tools used by the three Titans and Regigigas.

Pokemon/God Deity of
Regigias God of Creation
Regirock God of Stone and Construction
Registeel God of Steel and Metalwork
Regice God of Ice and Art
Arceus God of Protection, Weapon of Regigias
Dialga God of Time, Weapon of Regice
Palkia God of Space, Weapon of Regirock
Giritina God of Portals, Weapon of Registeel