You decide to sacrifice yourself and scout what's in the tunnel that has just opened before you and let your brother stay here hopefully. Your brother is speechless and just hugs you in respect and as your last goodbye from what it looks like. With uncertain expression you approach the corridor gates and just when you're about to enter you catch a glimpse of a silhouette in a lab coat and with some kind of needle gun or a tranquilizer. You immedietely regret your decision and are too affraid to confront the man, so you rush back in the direction of your brother.
"You didn't think it would be so simple as to leave, or make it easier for one of you." - Said the voice again with a slight hint of pride. The second you heard him say that sentence and before you even ran a few steps you felt a prick in your shoulder. You got hit with another metamorphosis dart and you froze in place. Not only because of pain that started building in you but of the hopelesness of it all, you didn't know if you should try to quickly find a plan to escape with your brother or if you should storm the scientist in the corridor again, now that you were already injected with transformation serum it didn't matter much.
Before you could estabilish the best option you were hit with a huge wave of pain coming from your spine. You tried to get to your brother but stumbled and fallen onto your chest, as you weren't able to catch yourself with your hands. You felt completely paralized and writhed on the ground in agony, turned around and tried to get up but your hands didn't budge, as well as your legs. You tried to cry for help, but when you turned around you saw a green-gray pattern of scales spreading from the spot where you had a dart in your flesh. With horror you realised what was happening to you. You were at best turning into a reptile and at worst into some snake, or any dangerous reptile abomination. Instead of screaming for help you managed to holler at your brother to run throught the opened gates, or to hide, run, anything! "If I lose control and slay you I'll never forgive myself, just run, this is hopeless, leave me alone to rot here! You gotta try!" Is all you managed to say before you felt something emerging from your tailbone and when you looked back in panic to see, it was a tail, slowly extending your length with each second. The pain then moved to your arms and slowly you saw them getting absorbed into your torso, and your legs melting with your ever-extending tail that was now one meter long, you felt them getting squished and disfigured until you were left with no appendages except your torso tail. You were getting longer and more slender, helplessly watching it all with your still human-like head. You didn't even notice when your clothes torn asunder, because surprisingly while you were transforming, you didn't seem to get any smaller into a regular snake size, you were much longer than your brother's height already and still growing in lenghth, each rib crackin and making you whimper in pain. You were almost entirely covered in dark scales which stinged your skin while emerging from it like a wave of spikes. The scientist only laughed as he saw your brother getting a panic attack, he really was enjoying this show, and sounded surprisingly like someone you've already heard... WAS HE THE VOICE IN THE CHAMBER ALL ALONG? The person teasing you and mocking your existence making you choose what you and your brother would transform into? It had to be him. You tried to move once again, but weren't used to slithering and just turned around onto your back and then saw something you completely forgot about. Your dick is also affected by the changed and you suddenly feel a burst of pleasure as it stands up and slowly becomes two penises which slide under your scales as you continue changing. From the neck down you became a complete snake. You knew what change was coming next, above your nonexistant shoulders you felt two bulging growths forming under your neck and as you tried to flex them you realized they were forming your hood, you were transforming into a cobra. Which would be fascinating if you'd see it in a movie and not from first person perspective. You choked for a while as your neck adjusted and lenghtened and thinned at the same time, hood finished forming. You then felt a horrendous headache as your head compressed in size and thinned out as well, your teeth falling out while you coughed blood from your gums. Your upper canines instead of falling out slowly morphed into spike-like fangs, above them you felt something churning as if it was your saliva but in your upper mouth, in truth it was your venom sacs developing and connecting to your fangs, you felt them getting cold filled with venom. You cried in pain as your entire upper face became more blunt and your nose connected to your upper lip and started growing out into a snake snout. Your have ears meld with your skull and became small holes in your head which provided hearing. Your tongue feels like its compressed as it gets thinner and splits at the end, and then slides into a "tongue tube" inside your mouth, ocassionally probing air around you. Your skin changes color and gets penetrated by the scales that grow out of your head and cover your entire body by now. As you noticed before you became a surprisingly big specimen of cobra. Which wasn't the worst part, for a second after the transformation you were terrified that you would lose your mind any second now. But then you noticed, the syringe-dart that hit you was still stuck into your back between your scales, half broken. It must have been destroyed when you were turning around on the ground, you broke it and some of the transformation serum didn't get into your blood system, maybe that's why you're not a mindless animal. You are a snake but at least you kept your human mind and you're not the size of a snake from Harry Potter, but still quite big. The scientist satisfied with your completed transformation, didn't even notice that something was off, or that the syringe broke. For a second you just watched your brother shiver and the scientist full of himself wave at you. "What are you looking at mindless beast, obey and devour your past brother, this instant" - Shouted the scientist. THATS IT, you could pretend to be what he just called you and trick the scientist and maybe escape this prison with your brother, since you still had your humanity in your mind you would probably be able to accomplish that. You shake your massive head dramatically and stretch your cobra hood and slowly start to slither closer to your brother, scientist clasping his hands together with a grin also steps closer satisfied that his serum worked. You both creep closer your brother and you hiss theatrically to show off. Your brother steps back in a steady pace until he falls onto his back tripping over a cable near the wall. "Kevin, I know you're still in there, I beg you stop this, defy this madness, we can escape, I'm your brother" - He cried as you were just a few meters next to him. "See Mike, there is no escape, it's all just a scene for a specific audience to watch this drama show. You and your brother experience painful transformations, will any of you survive, will you kill each other? What will you transform into, how interesting the process would be? But that's one thing, the second thing is that this is all recorded and we'll be sending it straight to the corrupt goverment as a proof of our serums. With them we could transform soldiers into animals that either rip everything they see apart, or what's the best part you have no idea of... Enough of this transformation serum could transform a person into an animal inside and outside, mentally and physically, but enough dosage could also only transform the physicall appearance of person and let them keep their human mind, which would allow our goverment to transform soldiers into animals and spy on WHOEVER they wish. This would make me rich, this would change the world!" - Scientist monologued and laughed hysterically. For a second you were lost in what he said and in the horrid truth, but then proceeded to go with your plan. Before scientist could say anything else you hissed angrilly and lept onto him biting him on his leg, your powerful maw wasn't big enough to eat it whole but you nonetheless kept the grasp strong and didn't let the scientist move. He tried to kick you off but you thrashed your head and made him fall onto the ground, your venom already far in his bloodstream, you've let the surprised scientist slide against the wall and let his leg go. You knew he was overwhelmed with poison and weakened so much as he couldn't even stand up. Your brother was twice as surprised as the scientist. "Oh my god, you're still in there, you didn't lose your mind, did you?" - Mike asked. You nodded and pointed the open corridor door with your tail. Your brother nodded and you...