An Overview of Sx
The Sexual Instinct, above all, seeks stimulation, whether it be physical, mental emotional, etc. This, most of the time, manifests as a want; a need for someone, to be intimate with and to fulfill their inner desires, or "make them whole".
When Sx finds someone, it knows it wants them, without hesitating to consider the consequences or background of the person. It wants unlimited connection and intimacy with that person, usually, but not necessarily in a sexual or romantic sense, and caters all their actions toward this person, e.g. making the first move in a relationship.
Some authors have sought to tame this Instinct with new names, such as Intimate or One-to-One, but any attempt at reworking the Instinct into something wholesome/spiritual/romantic misses the mark: the Sexual Instinct is an unbridled narcotic of wanting, untethered by ethics/morality.
The most common metaphor for Sx is a burning flame; a raging fire that keeps itself alive by seeking fuel to feed it. On the other hand, Sx can also be represented as rushing water; a river that seeks nothing more than to find its ocean, someone to lose itself into.
(impacts Sx dominants the most)
When healthy, Sx can deepen and strengthen relationships and interpersonal bonds, and steadily ringing intimacy levels to greater and greater heights until satisfaction; like a tight-knit family. The Sx user is adequately stimulated, and confident and caring towards their loved ones and intimates. They have a natural magnetism which draws people in, and can control themselves well.
Fixation and Stimulation
The Sx Instinct starts to become (what it deems as) understimulated and dependent on others, whether it be their close friends or acquaintences, to supply it with energy and life, much like a vampire. Instead of deepening their bonds, the Sx user starts to form "fixations", in which they not only want their person-of-choice's love and attention, but their "soul" as well. This can be overwhelming for some, and can ironically drive people away with the intensity.
Obsession and Desperation
The Sx instinct becomes drastically understimulated and desperate for love and/or stimulation, and would go to extreme lengths to attain it. This could lead the Sx user down dangerous paths, such as drug abuse or promiscuity. They become an "adrenaline junkie", and this attitude often puts off others and drives them away, and if the Sx user cannot find adequate stimulation to sate their desires, they will eventually sink into despair.
Sx in sx/sp
The sx/sp will only *truly* care about those they are close to, and try to push for more and more intimate relationships between people they already know. The energy from this type is given a laser-focused control by the sp, and seeks stimulation, but in a relatively safe way. This stacking is more willing to be friendly or "fake" soc, in order to attract potential friends or intimates. They build upon the (often few) close relationships they already have; many sx/sps have fantasies of whisking away their loved ones to a secluded place where they can do whatever they want, undisturbed by the world.
Sx in sx/so
The sx/so will often seem like they are driven by pure, uninhibited sx, luring people in and trapping them, much like a Venus Flytrap. This stacking is more prone to dependency, bringing awkward intensity into a group, and dragging "fixations" into it. It waits to see whatever looks nice to grab onto, and will fixate until either the target or the sx/so is drained. Sx/so might look desperate to others. Their energy is akin to battering-rams, charging into relationships and breaking walls until they fall, only to get back up again and continue bashing.
Sx in so/sx
The so/sx will have a similar charm and magnetism to the sx/so, but is generally softer and friendlier, ready to take things more steadily instead of rushing headfirst into things. The so/sx will enter a group, and scatter interpersonal energy (Sx) to a more focused area, and form close bonds with their people of choice. However, it would take a while for them to put their sx relations as a priority, and even longer for them to admit it (more commonly in Fe users).
Sx in sp/sx
Sx in sp/sx seems to be weak and almost non-existent at first, since they themselves always come first. They will never put somebody else before their own needs, even if they're their closest friend. Instead of bulding a castle with their close ones inside like the sx/sp, they build walls around themselves first, secretly hoping for someone to come in. However, this often puts people off becoming closer to them, leaving them alone.
Sx-blinds have a far gentler approach to interpersonal relationships, and are sometimes unsure and cautious in approaching someone they are attracted to. When in a close relationship, they may have trouble or insecurity in showing enough intimacy, and tend to compensate for this through acts of service(so) or advice and stability (sp) for their loved ones and/or partners. Sx blinds also have the tendency to "compartmentalize" their relationships, separating them and putting them into "boxes" (e.g. work acquaintances, online friends, real life friends, etc. are separated).