Genetic alterations were the new discovery and everyone wanted to make themselves perfect. Humans began to mess with things that shouldn't be messed with and it angered the gods. How they tempered with the creatures they made because they wanted better, filled with greed. So, the gods damned the humans and sent havoc on the world. The world as everyone new it changed and the people within it did too.
Mountains split open and began to unleash the hell below. Caged things that were meant to be in nightmares were unleashed. Creatures began to prey on humans and those humans realized too late that they shouldn't have messed with things that weren't suppose to be messed with.
And so, they took their science and altered their own genes to survive the wrath of the gods. Yet again, stoking the fire of the gods. The gods realized that humanity needed to be cleansed of their sins and the genetic altercations turned on them.
The humans that genetically altered themselves were cursed, binding them to their sins. These monsters had one sin that was more compelling than the rest and their goal was to do whatever it took for people to cave in to their own sinful ways. They were split up into seven groups: arrogance, anger, envy, sloth, greed, gluttony, and lust.
These human's genetics were bonded with their sins. Contorted and shown as the real monsters they were, those that were not genetically altered turned on them. They locked the beasts away and prayed for forgiveness from the gods, to stop the havoc and restore their faith.
Yet, the gods have no mercy and a final blow wiped out many of the humans; a warning to never do such a thing again. In the reminisce of those that were dead, laid bodies upon bodies that soon arose and made sure that the humans did no such treason again.
And so, decades passed and the reckoning carried on, humans forgetting all about the beasts that were locked up.
Until one day, curiosity killed the cat.