End of the World: I Was Expelled from the Shelter at the Beginning

A black rain shrouded the whole world, and all the creatures bathed in the black rain underwent changes.
They either became irrational monsters, or evolved!
Fit was kind enough to help others, but he was kicked out of the shelter.
In the face of countless zombies, he turned black.
He swore that as long as he didn't die, he would never be a simple good man!
When the zombies were besieging, the second black rain came. Fit resisted the erosion of the black rain and became an evolved person, and he also awakened his unique talent, Abyss Summon!
Fit: Since there is no law in the end of the world, let me give them the punishment they deserve!