Kos is a deceased Great One whose corpse is found in Bloodborne's The Old Hunters DLC. Although dead, in the throes of death it births the Orphan of Kos for the player to battle against. It is presumably infected by a number of kos parasites, seeing as the Orphan drops one upon its defeat.
The being named Kos, or sometimes Kosm, was apparently revered by the Fishing Hamlet's inhabitants, who were also mutated by her cosmic power. Some theories say that she was washed ashore after dying by unknown means, and the villagers began cultivating the parasites within her corpse, altered by their cosmic nature. Others believe she lurked off the shore, and sent the villagers the innumerable squids and fish in return for their worship of her.
In their search for eyes, Willem sent scholars from Byrgenwerth to hunt the villagers and investigate the nature of their transformations, brutally cutting open skulls so to extract their eyes. Whether or not they had a hand in the death of Kos is unknown, but most agree that the hunters did some blasphemous violation of her body, likely by dissecting her to get her eldritch blood. Only one hunter, Lady Maria, was bluntly confirmed to have been part of this excursion, which troubled her morality to the point that she forsook the weapon she used to kill with, casting the thing into a well. Others that have been theorized to play a part in that hunt include Laurence, Gehrman, Ludwig, and Willem himself perhaps.
But while the body of Kos rotted on the shore, the mind of the Great Ones is unending, and from the vantage of the cosmic planes she laid a curse upon the hunters. Those like the ones that desecrated her and the villagers, seeking to relish blood and eyes, would be cast into the Hunter's Nightmare. Engaged in an endless hunt, it is something that no hunter can escape, and it was implied that certain individuals would fade into the Nightmare at random, implying their life deeds to be especially punishable.
Though it is not clear why, killing the essence of her wizened child breaks the curse, freeing it into the ocean and pleasing the offended parties.
- If you look at its face, it appears unusually human-like. She even has a human face.
- Since the existence of Kos and possibly that of its son; an abomination born totally formed and all too human-like instead of being similar in appearance to a celestial child, is referred to as "the great sin of the fathers," it is possible that this Great One was the first attempt to transform a human into a superior being.
- Although Kos, or some say Kosm is whom Micolash beckon. Maybe it was Oedon that elevated Rom, the Vacuous Spider since Kos was dead.