You'll lead the legends behind Wicked Jester through a series of levels that comprise stages based on the four elements of water, earth, air, and fire. Each culminates with a different boss battle at the Psycho Circus itself. Along the way you'll collect each Elder's special armor (consisting of gauntlets, boots, belt, vest, plate, and mask), meaning that by the end of the stage your character will look just like his corresponding member of KISS. Your final objective is to destroy the Nightmare Child, which according to your tour guide through all of this, gypsy stereotype Madame Raven, is really, really bad.

Each Elder starts with a unique melee weapon (the Starbearer uses the sword-like Thornblade, and the Beast King uses the Wolverine-inspired Beast Claws, for example), and moves on to a selection of generic FPS guns. There's the machine-gun-like Zero Cannon, the shotgun-inspired Magma Cannon, and so on. The only variations are the cool Ultimate Weapons, which do massive amounts of damage, and the Scourge, a whip that can be used to both lash enemies and climb buildings and cliffs. There are a few interesting additional items in the game, however. The explosive Jack-in-the-Boxes and speed-boosting Black Diamonds are just two of the more intriguing devices you get to play with.

Game design is evocative of the original wave of first-person shooters. Meaning that the story and atmosphere take a backseat to the adrenaline rush of slaughering as many disgusting beasts as possible. It's a lot like the original DOOM in this regard. Where id's prototype sent wave after wave of fearsome demons at you from start to finish, Third Law confronts the gamer with wave after wave of surreal villains drawn from a psychotic's fever dream. This is accomplished by the generous use of Spawners, dimensional gates that bring in an unlimited number of enemies for you to blow away or slash to bits. These foes include the main shock troops, a spider-like thing called the Headless and a fire-spouting demon dog known as a Grunt, and all manner of bizarre circus-related opponents. Amongst many others is the grotesque and strangely pathetic Fat Lady, who tosses bouncing blobs of fat at you; the Strongman, who smashes the ground with the weights grafted to his wrists; the Ballbuster, who shoots cannonballs from a cannon where his left arm should be; and of course the Arachniclown, who has the body of a spider, the head and torso of a clown, and the ability to fry you with lightning.

While the weird and varied nature of your opponents and their domains provide a lot of character, gameplay becomes repetitive in short order thanks to the Spawners. Every level turns into a frustrating crawl. Think trench warfare, FPS style. As rushing into the fray guns a'blazing will get you killed in short order, you have to creep forward until the next Spawner comes into view, then try take it out from a distance before it starts to call in backup. Well, before it starts to call in too much backup. This nicely removes a lot of the frenzied bloodlust that made its DOOMy predecessors so exciting.