Baccano!

Aboard the Advenna Avis in 1711, a group of alchemists summon a demon in the hopes of gaining eternal life. The demon gives them an elixir of immortality and the method of ending their existence by "devouring" one another. Soon after, one among them begins to devour his companions. Realizing the danger posed by staying together, they scatter across the globe. Centuries later in 1930's America, a ...