Serina: Kraviathan (Patreon)

As the hothouse era has progressed, the seas have gradually become filled with all manner of life once more; trickling down from the coasts, creatures like whelicans, sea horses, brutes, and whiskerwhales have evolved over millions of years and now join pretenguins, sea dragons, dolfinches, and shimmershiners among the denizens of the salty depths. But in doing so they have entered the dominion of the most terrifying mega-predator in the world. Growing up to sixteen metres in length and nearly forty metric tonnes, with a pair of jaws up to three-metres long, this is the largest and most powerful invertebrate to have ever existed.

An adult kraviathan is the undisputed apex predator of the seas, far exceeding the size of any of its prey. Able to hunt virtually anything by itself, it has largely given up the social lifestyle of its calacarna ancestors, spending most of its life alone and nomadic. This is not to say it has entirely forsaken contact with others of its kind, for it can emit powerful vibrations through the water by grinding its pharyngeal teeth, which are picked up by its fleshy barbels, allowing it to communicate over great distances without ever needing to see one another. Despite its independence from pack-hunting, it remains an intelligent animal that requires occasional social stimulus. Occasionally, kraviathans have been known to work together to hunt especially large groups of prey, working cooperatively to drive the more vulnerable members of a shoal out and then sharing the kill.

A kraviathan is a keystone species like no other; its existence has driven the evolution of formidable anti-predation defences in contemporary animals. Huddling in great numbers, prey such as shimmershiners and sea horses have evolved to breed fast, live in highly social groups, formidable physical weapons such as spines and armour-plating, and defending one another vigorously, mobbing the much larger carnivore together with ferocious bites and body slams whenever it is sighted. The kraviathan in turn has become a superb ambush hunter; its skin can change its hue to match the undulations of the waves, allowing it to become nearly invisible despite its gargantuan size. Once within striking distance, its immense seven-metre fins propel the predator forward with powerful acceleration, striking its target head-on, usually killing the prey almost instantaneously.

In the most remote corners of the Unbroken Ocean, kraviathans sometimes gather in great numbers to socialize and court one another. Curiously, they tend to be lifetime monogamous, with females returning to the same males time and again, although they remain apart for nearly all their lives outside of this brief period of courtship and mating. Females give birth to a small number of pups, usually one to three, two most commonly, and care of the offspring is divided evenly between the two parents; if there is one offspring, it will be passed between the two parents every few weeks, but if there are multiple, they will be divided between the two parents. This helps alleviate the stress of caring for their offspring and teaching it to hunt, allowing offspring to learn survival strategies from both or either parents.

Young kraviathans are born already nearly three metres in length and become independent at around six to eight months old. Independent juveniles are much more social than adults, living in pods in shallower waters of the Equinoctial Ocean or closer to the coasts, mostly hunting smaller shoals of baitfish and escardines similar to smaller calacarnas. Because a full-grown kraviathan has no natural predators and can live for well over a century, they breed seldom and take decades to reach sexual maturity. They may spend over twenty years hunting in the shallows before becoming large enough to venture into offshore waters to hunt much larger prey and take another two decades before first mating. Adolescent kraviathans entering the open ocean are vulnerable, not just to the larger marine predators, but to their future potential prey, such as shimmershiners and dolfinches, which will often take the opportunity to kill the juveniles before they grow large enough to become a threat. Once mature, a kraviathan has virtually nothing to fear and becomes untouchable to practically anything but another kraviathan.