A considerable rise in the number of cognoscynths came in the time of Old Earth that marked an event so singular that it demanded the naming of its own epoch. This is the period that marked the psi-wars with it not being well taught in later years as none wanted to remember a time when Psychic Powers nearly destroyed the world. The unique powers of the cognoscynths meant that they became addicted to power and their own ambitions as they believed that they alone were capable of controlling the destiny of the Human race. They held the power to invade the dreams of sleepers and alter their mindscapes. At some point many thousands of years ago, the ancient cognoscynths raised the City of Sight with their knowledge of psychically-attuned architecture being unrivalled and hard-won after a long-forgotten age of devastating psi-wars.
Eventually, it came to pass that the great states learnt that they were simply pawns to powerful beings who set nation against nation as part of some savage amusing game. According to legend, a great warrior emerged with golden eyes who was the only one strong enough to resist the influence of the cognoscynths whereupon he rallied the armies of the few remaining kingdoms whilst training a cadre of warriors unlike any seen before. Together, they stormed the citadels of the cognoscynths whilst on the back of great silver flying machines with none of the cognoscynths being able to dominate the golden-eyed warrior. Everytime one of these powerful psykers were killed, their hold over the enslaved armies fell and the freed warriors escaped their bondage where they willingly joined forces with their saviour. It took thirty years before they managed to bring down the last of the cognoscynths who was slain thousands of years ago thus freeing the planet from their tyranny.
On the fate of the great warrior, some legends claimed that he died in battle with the final cognoscynth whilst others said he tried to claim power for himself but was killed by his men. According to some legends, it is said that the saviour still lived amongst mankind and awaited the day when the power of the cognoscynths would return. With the last known cognoscynth slain, their discipline and arts became extinct alongside the skill of crafting psychically resonant structures had followed them. The dark history surrounding their kind led to numerous rumours and legends on their powers with some believing that they are exaggerated. During the time of the Great Crusade, it was believed that the power of a cognoscynth could not be used without a single operative of the City of Sight becoming aware of their existence.
These psykers had a unique and uncommon mutation that only occured in one in a million being being born with a latent power. Out of these, only a tenth had the capacity of actually harnessing this ability with the gene-code being two orders of magnitude rarer. This meant that they are considerably rarer than any normal psyker with a unique power. The most notable ability of the cognoscynths is the fact that they can maintain the first sensation and connection the warp without feeling psi-sick. Unlike normal psykers, they are able to touch the warp just like the first moment and became addicted to its power. According to legend, it is said that these psykers were virtually immune to the dangers of the warp and that no immaterial creature was capable of touching them. There was little that they could not accomplish as their power allowed them to control the minds of people and making them do anything.
Their power allowed them to go into the mind of a person where they are able to override their innate sense of self-preservation along with their understanding of right and wrong. They are able to turn a person into a puppet with almost no effort and compel them to do unimaginable acts of horror whilst laughing. Cognoscynths are equally capable of erasing memories, grafting new ones and make a person feel what they desired them to feel. Some legends spoke of the cognoscynths even having the power to open gateways in space and time.