My take on the Cockatrice was inspired by an artist rendering I saw once for D&D where the creature looked very emaciated and sickly which gave me a flood of ideas I've incorporated into my concept.
In the world of Macabre the Cockatrice are voracious eaters and highly venomous. They in fact pose such an extreme danger that they are avoided by all other creatures in the world, even ones 100 times their own size.
They don't even like their own kind and are most often only encountered as lone wolf hunters. Thanks to this however, their numbers are exceedingly small. No one has been able to figure out how they reproduce.
These twisted reptiles have several unique aspects that make facing them down in combat a near certain death.
First among them is the Cockatrice gaze. Cockatrice eyes are like no other. They are packed with pigment cells and bio luminescent bacteria that the creature can control in remarkable ways. The eyes when spotting its prey activate into a radical light show of patterns and colors that send their soon to be victim into a dazed state.
The creature in effect hacks the brain of its prey via light patterns that adapt within seconds to its victims physiology. It has a 100% chance effectiveness, so long as its prey is capable of seeing its gaze. Many creatures in fact know to look away no matter the cost from this unique attack. But the Cockatrice has tools to make even this more difficult.
Cockatrice tail feathers have incredibly striking patterns that are also constantly shifting due to mechanisms with that are similar to the Cockatrice eyes. While the tail feathers do not bear the same dazing quality, their pattern tends to be such that most creatures feel compelled to star into their pattern. Which the beast then uses rhythmic motions of its tail to slowly draw its prey back to its true eyes. With these 2 mechanism the cockatrice is able to swiftly close in on their prey before they even realize the danger their in.
Most usually the Cockatrice will consider any creature largely composed of meat to be a viable food source, their size of no importance. They will attack creatures as small as rodents, to creatures on par with the scale of a Lesser Dragon. And whats more startling is that they just as effective at hunting giant prey as they are anything smaller than themselves.
So long as as it can be gazed the Cockatrice can take it down. by utilizing its next set of deadly weapons. it's not known what Cockatrice beaks are made from but they are believed to be on part with diamond forged blades. There isn't anything that a cockatrice can't bite through given enough time to work on it.
While their bite forces isn't the strongest known in the world, they can, when given enough time, cut through even the thickest armored hide. Once that razor sharp beak pierces the body unique toxins within the monsters saliva cause a radical fibrosis of their preys muscle tissues. In effect turning their body hard as rock.
The process takes seconds to petrify limbs and only seconds more to spread through out the rest of the body. Gigantic creatures can take upward of a minute before they are completely turned to stone. This allows horrifying property ensures that there isn't anything that a Cockatrice can't take down eventually. But it comes at a severe cost to the cockatrice.
The personification process occures so swiftly that most usually the creature is lucky of their able to bite off and swallow even a single bite before their prize is too hard for them to consume! This leads to most Cockatrice looking incredibly emaciated, they are constantly starving and seeking food, but whats worse is that they are incapable of dying from this.
No one knows what alchemical magics were used to imbue the cockatrice with such properties, but as far as anyone has been able to observe cockatrices are immortal. It takes an exceedingly large amount of damage to kill one permanently. They've been observed being crushed flat by larger prey that escaped, only to be able to shake off the injuries within a few short minutes. They can't die from starving to death like other forms of immortals. They are cursed to forever roam the world in a continuous state of suffering.
These properties have made the species of intense interest to the Lichs of the inner council. Who spent centuries trying to unlock their unholy dice role of supernatural powers. Several were turned to stone for their efforts. If you should ever encounter a well fed or worse a fattened Cockatrice you should be very worried. As the only way one could ever get fat is by being fed by some unscrupulous party who will not have your best interests in mind.
The only proven method for killing a cockatrice is to cut off its head, which is easier said than done given their intense speed and a physical strength that belies their malnourished frame. The razor sharp quills and talons all over their body also contains potent neurotoxins that are capable of temporarily paralyzing flesh should they succeed in piercing flesh. This toxin will almost instantly cut a victims speed in half, which will most assuredly spell doom for the combatant.
Cockatrice parts are always in high demand in all parts of the world, and their heads always demand the highest bounties from local fiefdoms. That is, so long as their willing to turn over the twisted things head. otherwise they can only claim a small percentage of the true value. This had lead to at least one slayer having made a career of traveling the world and getting paid partial bounties for the same head.