A second wave of disaster struck the world 20 years after the first disaster. The only difference this time was that humanity was both better off, and also worse off. All guns ceased to function, it doesn't matter if it was kinetic weaponry or energy weaponry that used the crystals that monsters dropped (which were in short supply after 20 years). Both types of weaponry completely stopped working, missiles and tank shells also did not work. Explosives still exploded, but when they were made with the intent of shooting a piece of metal at 300m/s they did not explode. The only thing that could fire were bows and crossbows. In exchange for weapons ceasing to function was the second generation's powers. They used them valiantly and killed hundreds of monsters, humanity was better off, they were experienced since this had happened before and casualties were at an all time low. Only about 40000 humans died before the spatial rifts were closed using the devices that had been improved upon in the 20 years. Just in case. It was a good thing that they did.
But then only a year after that the rifts opened again. There were even less casualties, and the rift was closed.
And then they opened 2 months later.
And then 1 month later.
And then 5 days later.
The good thing was that the rifts only contained weak monsters which could easily be dealt with, most of the time.
These rifts ended up being called dungeons. These dungeons could be ranked into six categories using the alphabet.
F
D
C
B
A
S
These were the tiers of the dungeons, the strength of the monsters determined what rank a dungeon would receive. Humans with abilities also received rankings on the same scale. However they were not on the same power level. A single F ranked human could not deal with an F ranked dungeon, they could at most deal with one of two monsters from the dungeons. But that wasn't a big problem, since every single human that was a second generation had at least an f ranked ability. Of course there are exceptions to all rules, a new tier that was rarely seen was made for humans.
T- Trash
It was even below F, Trash were second generation humans with absolutely no ability. Even if you had an extremely weak ability, even if all you could do was blow a cool breeze towards an enemy, you were still considered above Trash. Of course other than the degrading name there wasn't anything that was too bad about being Trash. Trash was also a slang that the second generation came up with, it was not officially official but it had become a very common term. T tiers were treated the same as first generation humans, they could live a normal life, albeit with a bit more humiliation than normal, but that was all. Some would argue that being an F tier would be worse than being T tier, since F tier would be forced to participate in hunting monsters whenever rifts showed up. While T tier were allowed to hide, and had no responsibilities.
If you were an S tier you could live in luxury, but you also had to fend off monsters, and you would be required to fight S ranked dungeons on the rare occasion that they showed up. And keep in mind that even if you had an S ranked ability, you would still be fully human, which means a single swat of a monster could kill you. But obviously there were many exceptions to this too. The monsters started dropping crystals again, and these crystals were used to make various armors, and even elixirs which could improve constitution and let you survive a few hits.
The rate at which dungeons appeared settled down into a steady rhythm, the dungeons were no longer a worldwide phenomenon anymore either, they only appeared above cities randomly one or two at a time. Small towns were completely abandoned and everyone moved into super cities across the world for safety. Monsters roamed the wilderness but it was manageable. Humanity had adapted and found a way to survive in the end. Slowly the first generation grew older and the second generation continued fighting the monsters, that is where our Main character Tristan comes in.