“These unholy clockwork things are everywhere!”
“Take to the river! The water will rust their gears! Then we’ll—aw, crud.”
Clockwork submarines have been a staple of adventure stories since Twenty Thousand Leagues Under the Sea. Seems only fair that clockwork leviathans should get their time in the spotlight. (Check out the breath weapon! And that really nasty grapple attack!)
One of the tricky things about constructs is that, if you adhere strictly to the rules, many of them can only be created by spellcasters of vastly greater power. This is obviously for game balance reasons, so PCs don't wind up at the head of an army of golems. But it can also strain encounter level design and suspension of disbelief—you don’t want a party of novice adventurers running into a 12th-level mage just because they demolished his clockwork soldiers.
So if you’re a stickler for detail, good news: The clockwork leviathan is one of those rare constructs whose CR matches its minimum crafter level exactly. So after PCs smash Pinocchi-Eel, they can knock down Geppetto’s door the very next encounter.
When threatening the vengeance of the gods, it helps to have that vengeance at your command. Apocalyptic preacher Cranston Mowles uses a clockwork leviathan to compel obedience to his millenarian cult. Cultists who waver in their faith are quickly dealt with, as are any instruments of the law or mainstream religious leaders. Mowles also keeps his cult’s finances strong by discreetly aiding local ship captains in attacking their rivals—a lucrative sideline. While Mowles is sincere in his beliefs, his growing greed may be what first brings him to an adventuring party’s attention.
The ocean moon of Shells is so dubbed because it appears to have no proper surface at all—the “land” is composed of the fossil shells of castle-sized cowries and bivalves. Spacefarers who land on these great cockleshells do so at their peril, as the shells often hide clockwork leviathans. Certainly there are secrets at work here: Who made these leviathans? Where did their metal components come from? Who still winds their keys? Clearly, some dark vessel or even a foundry must lurk below the waves.
Other constructs of Cognomon clearly have a purpose—or did at one time—no matter how bizarre or inscrutable. But the World-City’s clockwork leviathans seem to defy any logic whatsoever. Typically the eel-like machines burrow randomly through Cognomon’s underrealms, drilling deep holes to nowhere and terrorizing the unfortunates who live in the Below. But they can and do erupt from anywhere, even the most secure market towns. (Strangely, they tend to avoid androids—one of the only reasons the machinefolk are tolerated in some settlements.) Sages’ best guesses posit that clockwork leviathans are part of the World-City’s immune system…or a symptom of the Clockwork Mind’s madness. Skum, too, combat the amphibious leviathans ferociously, though their aboleth masters often reprogram the constructs as war machines. Incidentally, skum writings use the same word for clockwork leviathan that they do for the parasitic nematodes found inside the guts of fish—suggesting that skum believe the entire World-City is nothing more than the digestive tract of some truly monstrous clockwork beast.
—Pathfinder Bestiary 3 55
Looking for clockwork leviathan imagery for your tabletop is probably the only reason on Earth to see Transformers: Dark of the Moon. At least that’s my theory, having refused to see Transformers: Dark of the Moon.
Are any of you World Cafe fans? Sam Sessa, who I used to live with, got interviewed by David Dye, who I once got drunk with, about the songs he plays on the station I used to work for. The link is here.