This wondrous summoning art was not a method of the Church of the God of Knowledge, but had been bestowed by His Majesty Void Mask. It was said that His Majesty Void Mask called this summoning art "Grand Construction," though no one knew what that meant.
To perform this summoning art, one first needed to build an altar, then place four types of resources upon it: gold coins, gemstones, steel, and materials taken from various creatures.
These materials had a basic unit of measure, called a "unit." Thirty units of each type were the minimum required to complete a summoning. Converted into gold coins, it came to roughly a hundred gold coins.
After enough resources had been placed upon the altar, one could conduct the summoning through a fairly simple ritual. The ritual consumed the resources, and a divine envoy from the divine kingdom of Shelter would descend into the mortal world as a dependable helper.
Though these helpers were only temporary and would return to the divine kingdom after a while, they were not only powerful, but also very beautiful. As comrades-in-arms, they could hardly be more reliable... and they were pleasing to the eye as well. Thus, although this spell had yet to spread officially, it had already become immensely popular among the senior members of the churches who knew of it. Nearly every high-ranking cleric of the Void Mask Pantheon made a point of learning this spell and would use it when needed, summoning divine envoys to help.
Generally speaking, the more resources one used, the more powerful the divine envoy one could summon. But among the divine envoys was a special class of elite envoys. They were vastly stronger than ordinary divine envoys, yet the cost of summoning them was no different from that of ordinary