To help you deal with the "ongoing onslaught of Grims," as Insomniac CEO Ted Price put it, you'll have the assistance of the Sledgehammer. That's not a codename for some kind of missile -- it's an actual sledgehammer.
Helping to darken the setting even further is a seven-song soundtrack provided by metal band Mastodon. "But wait," you say. "Isn't metal totally anachronistic for a game set in 1957?" Of course, it would be, if the characters heard it. Also, all metal musicians are actually aliens. Somewhere in the back of your mind, you already knew that. No human can play drums that fast.