A mysterious Unicorn makes a portal to the Mojave Wasteland, the balance of power in the Mojave is slowly shifting to an unknown force.
A power even stronger than Mr. House, even stronger than the NCR or Caesar's Legion. Factions from all over are being wiped out, there was no one to stop this threat.
The Wasteland would need an army.
Or a trigger happy mailman and an ex-unicorn with magic.
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This is just a side project for a friend and to keep my writing skills(like I have any) sharp until I can figure out how the hell I'm going to finish the new chapter of Why Rainbows Make Me Cry.