The Shot-Gun Arcana (Golgotha #2) by R. S. Belcher
Synopsis from GoodReads:
1870. A haven for the blessed and the damned, including a fallen angel, a mad scientist, a pirate queen, and a deputy who is kin to coyotes, Golgotha has come through many nightmarish trials, but now an army of thirty-two outlaws, lunatics, serial killers, and cannibals are converging on the town, drawn by a grisly relic that dates back to the Donner Party…and the dawn of humanity.
Sheriff Jon Highfather and his deputies already have their hands full dealing with train robbers, a mysterious series of brutal murders, and the usual outbreaks of weirdness. But with thirty-two of the most vicious killers on Earth riding into Golgotha in just a few day’s time, the town and its people will be tested as never before—and some of them will never be the same.