Efficiency

Can't ever be too careful, even when dealing with lower species.

The tissue weaves inelegantly into what you need it to, but with the expertise of an artisan, you can shape it into what you need given enough time. You wrap the borrowed genetic slurry and twine it, strands forming ropes which you shape into neurons and sensory organs. Your focus is on amenities, usability and convenience over anything else. You first form an extremely basic set of sensory organs. Visual and auditory senses that are a little more refined and consume a little less energy than your projection-based scanning. It also ensures that you can use your mind for other things at the same time as you observe. Functionality comes over form. You don't need external ears so long as you have holes that hear. You don't need teeth and a tongue so long as you have the feelers and pores to draw energy from your source. For visual senses, you must first build rods. Basic sight cones that can divide the light from dark and create depth, but lack color and detail. On top of them, you build some basic lenses to focus with. You don't need to see on much higher of a level for now.

Bodily features are at a lower premium. For now, you don't need external reproductive organs or much in the way of limbs. Simple grappling feelers and ambulatory poles. No organs to create energy, leeching from the genetic code of hosts is enough to get by. The time may come when you breed with these primates, but that remains in the far future.

The transformation is exhausting, but your clever usage of your time and resources means it doesn't take long. When you puncture your way out of the fleshy egg you've constructed around yourself, you stumble around on your new ambulatory tools. You are a wobbling, fleshy flatworm on a great number of unjointed legs. No more than a foot long and with a body like a deflated balloon. Your simple legs can propel you rapidly, but you need to turn your whole body slowly to get anywhere. You gave yourself a sharp little pointed weapon arm with a complex gland at the core of its stinger. The gland is currently empty, but if you needed to, crafting any number of venoms or toxins would only take seconds.

You skitter quickly through the crack underneath the door. Outside of the room is a narrow passway with another door directly across. Stairs lead down on your left and another door sits to your right. You poke your head under both doors, one is a room with a basin to collect water as well as a waste removal device. The other is simply a closet full of ratty clothing and a pair of stored weapons similar to the one that killed your old form. A four-legged rodent peers at you with beady, untrusting eyes. When you advance toward it, it lunges at you, clearly not seeing you as a threat.

A foolish creature.

You immediately open wide enough to swallow the thing twice over, it only has a moment to consider the grievous error it made before you swallow it whole. You absorb it into your body and release the carcass in about a second, leaving a dried husk where it once stood. The genetic information you gain from it is effectively useless, considering the lowness of the being; however, the energy you get back is a welcome refresher after an exhausting transformation.

You slink back out into the hallway and writhe your way down the stairs. The simple wooden floors are coarse and old, providing a near-infinite number of little footholds and places to grapple for purchase.

At the base of the stairs is a room with an electronic box, broadcasting images that seem to be in black and white... though everything you can see is in black and white so it's hard to tell. A young woman lies half-dozing on a cushioned seat in front of it. You note her as a backup option, but your new form is more suited for a male host. Luckily, you hear some noise from a room immediately to your left. When you poke your head under the door, you see a young man out of bed in a state of half-dress. The soft dusting of hair on his face and body tells you that he has just recently reached adulthood. The strong pheromones coming from him reinforce that. He has much less fat on his body than the older male upstairs and has a quiet spring in his step.

You dart under his bed, waiting for him to stop to admire himself in the mirror before you jab him with your stinger. The hastily brewed concoction makes him collapse backward onto his bed, hopefully still alive. You quickly slink up his leg into the wide bottom of his loose-fitting undergarments. You quickly flush your old venom and brew a new one. You spread your basic mouth open and slowly fill your hollow body with his sex organ. You give his balls a quick jab with your new venom, sending him into your best estimate of what a human rutting pattern would be. His cock immediately swells up, the rush of alien-induced hormones causing his anatomy to expand beyond the previous limit. As his testicles start to fill to the limits of their natural capacity with sperm, his cock rises to attention. You reshape your body to form a near skin-tight seal around it.

He groans, the first hit of venom starting to weaken. It was a powerful but short-lived dose. He tries to stand, but his legs give out under him at first. When he finally manages to stand, he pulls his boxers off with an incredulously shaky hand.

"What's... happening?" He groans. His organs swollen to painful new dimensions and your jet-black body obscuring his sight of the organ that formerly belonged to him.

He reaches out to touch you and immediately recoils at the sensation of your rubbery exterior. He lets out a whimpering noise and draws his hand back like touching you burns him.

You start to contract your inner muscles along his shaft in steady pumping motions, squeezing upward starting at his base. His legs wobble again and he falls back into his bed, his eyes going hazy. The surge of overwhelming seed that pressures his body to be released causes every muscle in his body to jerk. He arches his back, trying to thrust up into whatever phantom stimulus is working his body. With your mind and his linked, you watch disinterestedly as his mind goes from anger to fear and then immediately to desperation. The pressure in his balls is intense enough to make him feel like he's going to pass out.

In only seconds his first orgasm comes spraying out like a depressurizing shuttlecraft. With each heave of his mutated balls, his body tries to everything it has out in a single pump. With each jerk of his hips, he empties enough cum into your feeding systems to fill a human womb twice over. With each pump, however, his balls replace what he jettisons near-instantly. Even when he realizes that his release isn't slowing down, he can't stop himself from within in pleasure. The bursts of genetic code and electricity you get from each pulse, even after a dozen, adds to the energy that you'll need to move forward with your evolution.

Eventually, even with augmented capabilities, he begins to near his biological limits. Even as his body continues to more and more cum out than should be humanly possible his life signs begin growing weaker. He lays in his bed with his mouth open, hoarse groans all that he can manage. His mind is fuzzy, it is nearing damage he can't fully recover from.

So once again, the question of evolution comes up.

With the genetic material you've stolen, you can finally evolve yourself into a "human-like" form. However, there are... limitations to your capabilities. If you make a new form from scratch, you can give yourself the genitals of both a male and female to maximize your spread. However, a created form is more conspicuous. You can only imitate an amalgam of forms you've seen, not create something entirely new.

Alternatively, it would be very easy for you to simply control the current host. You would spread to assimilate his body, either destroying her mind or leaving it intact... somewhere. You would only have one set of genitals, at least unless you built yourself another, which would be extremely limiting. You would blend in better but you would be under greater scrutiny from some and less than others, you would have to choose your next moves far more wisely.