As ineffable as any abstract deity, as uncaring and unyielding in its caprice as the whims of the most violent storm, the Yuluk is a perfect mix of opulence and violence.
Deep, deep down in fathoms unfathomable, in depths not reached by the sun’s boldest warmth and brightest glare, there exists an alien world the bounds and borders of whose mysteries we cannot begin to understand. Although the oceans cover over seventy percent of the world’s surface and teem with multitudes beyond imagining, almost everything we know - everything we believe we know - is limited either to the surface or, relatively speaking, to its shallowest reaches. Far beneath the rolling, roiling tumult of waves lies the preserve of monsters and myths, the greatest horrors of history and prehistory in silent but watchful repose.
To even get a glimpse of the things that lurk there is rare, scarcer in many ways than the most elusive of the ghosts or ghouls that haunt our nightmares. We may share a planet, but their world - a freezing, crushing darkness - would pulverise us before we even had a chance to drown. Most of them would fare just as poorly in ours, so just the fact of something crossing the divide and surviving is enough to show us that it is remarkable, resourceful, or both. If, like the Yuluk, it can do more - if it can thrive and command the thrall of any living thing it crosses - we can assume it draws some aspect of its strength from some supernatural source.
The oldest sightings of the Yuluk come from the earliest days of human settlement on the continent that the West would come to know as Australia (a land which, at the time, was home and host to a number of species of now long-extinct megafauna) but its distinctive visage appears to have inspired creatures of myth in cultures separated by thousands of miles and tens of thousands of years. Almost incomprehensibly enormous, the Yuluk is described an eyeless snake that shimmers in near translucence, its body covered in overlapping rows of scales that it can flare out and pull close; feathers made of barbed and razor-sharp diamonds.
Within this guarded transparency, this prismatic illusion of vulnerability, is the only solid colour that the Yuluk bears; its too-thin channels of blood like molten gold. It is unsurprising then, that it is believed to be the inspiration for the numerously named feathered serpent gods of several Mesoamerican religions and the Norse world serpent Jörmungandr - a monstrous child of Loki who is said to encircle and ensnare the world in eager anticipation for its part in Ragnarok, the twilight of the gods. Although its size is likely the most prone to embellishment and exaggeration, its pantheon-spanning inspiration can give us an idea of its commanding presence.
Nonetheless, there is some proof to suggest that its passage across the earth gouged out the channels that became major rivers and waterways. At the bottom of the Yangtze and the Congo, and even parts of the Nile (to name only some of the most famous sites), albeit often buried by the ebb and flow of sediment and shifting silt, people occasionally find scales loosened and shed by the Yuluk. Each more or less uniform in size, they have - admittedly - lost some of their legendary lustre in the intervening millennia, but they remain almost priceless as a result of both their mythical significance and their material value (being apparently, as they are, essentially indestructible).
Proof of the Yuluk’s presence in the deepest parts of the sea is more overt and more forensic. Not restrained - nor restraining itself - to feeding, the Yuluk also apparently hunts for the sport of it; testing its considerable mettle against anything large enough or dangerous enough to catch its attention. Ironically, it is responsible for some of the best evidence we have of other species of quasi-mythological aquatic life (some of whom were previously or remain publicly categorised as cryptids themselves), dragging the savaged corpses of giant squid and octopus and tank-like invertebrates to the surface or into shallower waters, bodies sometimes pierced with distinctive scales.
In spite of its aethereal appearance and undeniable vastness, the Yuluk’s imposing physical aspect only show it to be a pronounced outlier - perhaps still hailing from an ill-explored branch of the evolutionary tree. Instead it is in its increasingly infrequent sojourns to the surface that we have seen the behaviours that indicate that it is more than just an extraordinary beast: Faced with human interference or defiance the Yuluk can extend a quivering crown of its feathered scales to catch and manipulate the sunlight (its blindness seemingly no impediment to such an intricate physical display and, by dint of the patterns of colours, light and shade it chooses, bring any opposition to heel.
Both the physical delicacies and intellectual sophistication of such hypnotic abilities - which can be turned to brute force stupefactions and creating temporary fugues or to inducing an instantaneous and unshakeable bond of fealty - speak to something unique to our experience. The Yuluk does not have the necessary physiology to speak, but is clearly possessed of an understanding of abstract complexities that we must presuppose speak to a high-level linguistic function and the ability to communicate and command in - demonstrably - at least the dozen languages spoken at the times and in the places it has been recorded to have appeared and come into conflict with a human civilisation.
Having given itself no name, and setting out no grander agenda than taking whatever immediate gratification it gets from the senseless violence that attends it, what little we know of the Yuluk’s motivations have been gleaned from the speculations of those it has entranced. Their worship itself seems incidental - the religious trappings built around the awe vary too broadly to speak to a deeper desire. Still, several share the sentiment that the Yuluk is waiting for something, perhaps a true challenger to its power, and that its sporadic returns to the surface world are an endless search for whatever champion or nightmare will eventually arise to face it and to kill it.