Grendel Vs The Shadow #1 is coming from Dark Horse Comics this September by Matt Wagner. The series description, as stated by Dark Horse says:
Sparks fly and bullets blaze when the original Grendel, Hunter Rose, is transported to 1930s New York and faces off with the original dark-night avenger, the Shadow! Two pulp-noir icons go head to head in this three-issue prestige-format series written and drawn by legendary Grendel creator Matt Wagner.
You can see a first look preview for the series below! Pick it up from your local comic shop on September 3rd.