A parasite. Any organism that subsists upon the wellbeing of another. A leech. A vine. One would rarely think that a parasite could become a victim of another parasite and moreover to think that those two would feed upon one another seems to evoke a paradox. But this mutual parasitism exists more often than one expects. Day by day, I see these toxic relationships around me and even in the very relationships I am in.
Have you ever seen something become so intertwined with something else that it is no longer possible to determine which part is of one or the other? And eventually these braided existences cease being distinct and meld into a nauseating conglomerate of dependency? This is mutual parasitism. They become so engrossed in each other that they don't realize that they are sucking the life blood from each other until they no longer hold an individual identity. They no longer have the characteristics that make them distinct species. They become Monanthro unum, an organism that was once made of two that now are just halves. What they don't tell you about the Monanthro unum is that it is a species with no personality. It has become evolutionarily inclined to forget its natural behaviors in order to appease the organisms it becomes dependent on. It cannot think for itself in the singular form. It cannot decide for itself. Its absorption on its other half makes it forget of the external world because all they have the capacity to acknowledge is the mutual parasitism of the two halves. They lose touch with reality and they never reach a point of consciousness that allows them to break the malefaction that is their relationship. They become dead to the world around them.
But there is a secondary part of mutual parasitism. One that arises from a de facto connection between two species rather than a constructed relationship. It is because of this de facto cord that ties these two species together that they are forced to subsist on each other. Slowly they drive each other mad as they feed upon the livelihood of the other but they cannot stop and will never stop. They cripple each other and their ability to thrive. Slowly killing each other in mutually assured destruction.