The Thirteen Acts
The first act was the corruption of the veil, so that they God could go away.
The second act was the search for a new place, for they would need news warrens for all of their kin.
The third act was the consolidation of will, for they were traitorous even to their kings.
The fourth act was the gathering of wealth, for they would need it and it was a better deterrent of blades.
The fifth act was the building of the path, for the way was treacherous even at the best of times.
The sixth act was the fall of the land, for defeats and shame were not to be left to die.
The seventh act was the rebuilding of the well, for the seers would need clearer waters to sway.
The eight act was on the side of their God, for the trash and residue in then pile was greater than he thought.
The ninth act was also by Him, for he dropped the choicest recipes where they would be the best.
The tenth act was the by most the best, for the way was cleared of debris, the path was built without fear and He welcome them with darkness and chill.
The eleventh act was the most mundane, for the kin needed a place to work, sleep and eat.
The twelfth act was a most joyous day, for the sacrifices were slayed: A massive beast, a terrible plague, an ingenious artifact, a silent fiend, but this were just the start because the rest just would stand by, a great number of souls both man and not in chains marching to sacred doom, the plans for a vessel to navigate in the void, a hill of a stone so precious and wrong, two champions of war though different in face for one belonged at the front an the other throughout the earth, a million of kin pushed to the from and the grey form of a wizard wishing for the end.
For this act was to be for their God and he gifted a most sacred whore, who instead of Kin poured forth Sacred Stone
With all this complete and the plans hashed out, they all moved to begin the final and thirteen act.
But something was wrong with the glorious plan for a man from the skies had come to the dark and pillaged the knowledge that was clan by right.
And so, they moved to change, the armies and slaves, for the might of the skaven shall not be denied and they will crush this interloper under a Vermintide.
Author note: this is my attempt to explain this story, basically the Horned rat saw that the other chaos boys were not paying that much attention the real anymore and went to ruin the fun by finding the 40K universe and bringing his boys to cause more chaos and gifted them a modified breeder that instead of more skaven gave warpstone, only this time in his name, and left then under our hive city with all the STCs that he could find in a short period of time for them to discover, and then we show up to take them, they did not like that.
Author note 2: the 12 clans mentioned were Skryre (engineers obsessed with lighting), Pestilens (chemists that like war crimes), Moulder (biologists that admire Frankenstein), Eshin (assassins/mercenary's), Gritus (slave masters), Krizzor (beast masters), Skurvy (marines and ship builders now void marines and spaceship builders), Grutnif (alchemists that [at least in my version] can make warpstone better and stronger), Skab (frontline warrior clan), Gangrous (tunnel warrior clan), Mors (mostly brought there by the others for population) and finally Vechiare (a clan mostly made out of grey seers).