The First S-Rank Gate, as noted by its name, was the first S-Rank Gate to ever open and one of the most catastrophic dungeon breaks in history.
The gate spawned on the west coast of America about eight years before the events of the main storyline. As a S-Rank Gate had never been seen before, the American government prepared for the worst and offered a huge reward to any S-Rank hunter who was willing to tackle the gate. Despite the fact that over 100 S-Rank Hunters answered their call, none of them were prepared for what came next; the dungeon boss, a ferocious dragon named Kamish, emerged from the gate and laid waste to the entire west coast area, slaughtering scores of S-Ranks Hunters along with millions of civilians in his wake. His rampage only stopped when the last five surviving S-Ranks banded together and successfully killed him, finally putting an end to the mass destruction and death he had caused.
As recognition for their accomplishment of bringing down Kamish, the five surviving S-Rank Hunters were each given the authority equal to that of a nation's and became known as the National Level Hunters. Kamish was also given the epithet of humanity's greatest calamity and the amount of devastation and death he had caused served as a warning to the rest of the world as to how deadly a S-Rank Gate could be.