The influence of a Minor Treasure could only be unleashed through Prana. Therefore, to influence Virala's being, Prana was constantly seeping into his body from the golden giant's stomach. And it was being unleashed by twelve Minor Treasures.
These twelve Minor Treasures weren't the limit of the Brimgan Empire's stash. After all, Brandal Brimgan alone had fused with eight Minor Treasures. Adding onto powerful branch families of the Brimgan Royalty that had a Minor Treasure or two, their total number would be way higher.
But the twelve Minor Treasures had been selectively placed in the eye sockets of the golden giant, because their synchronised perfectly with the Major Treasure's influence and generated an effect capable of extracting information from the minds of anyone placed in it.