The day the world as we know it changed forever, the day the Gods gave up on mankind.
'The council has decided that there are too many planets for us to control, from this day forth you shall all be put under a test. There will be 100 levels of dungeons that you must conquer, if you fail to destroy the dungeon boss of the 100th level within 1000 years on nightmare mode, your race will surely perish. You will be able to access the tower from within your systems. However as a side effect of the tower; dungeons will randomly spawn across the world with increasing difficulty as time passes, if you fail to defeat the dungeon boss within then a dungeon break will occur allowing the monsters to run free. Oh, one last thing, no weapons from outside will be allowed within the tower or dungeons. Good luck, and may the odds be ever in your favor.'
The announcement was played across every humans mind at the exact same time, the events that occurred after this changed history forever. The governments were thrown into chaos, all clawing for an answer to their problems. Unfortunately for them, there was none.
After that there was chaos, as level 1 dungeons only took a week for dungeon breaks to occur, alongside the fact that their portals were as small as a car many went unnoticed, millions died as orcs and goblins descended on unprepared cities and towns, luckily bullets worked on these monsters, giving the governments enough time to build up walls around the cities and fight back.
However, there was millions upon millions of monsters and there was no way to take back the most barren of lands, so humanity walled up many deserts and jungles, designating them as forbidden zones. There was no way of telling the levels of the creatures within so hundreds of thousands of soldiers were station along the walls all the time, not allowing a single monster to pass.
When an explorer killed a dungeon boss they were given the option of respawning all the creatures within or getting rid of the dungeon, the governments built up academies to train the future generations centered around T1 and T2 dungeons. The government could no longer afford to discriminate between the poor and the rich, with the new world being centered around power, the stronger you were the higher your position was.
The training within allowed them to follow their own path of cultivation before entering the tower in an effort to save mankind, the fate of humanity rested upon their shoulders. If they couldn't accomplish this task... Every single person would die, our friends, our families, the people we hold dearest to ourselves... There was now one thing every race in the universe could agree upon... Fuck the Gods.