He had to finish this experiment by sundown. That was the unfortunate truth of holding his "lab" in a basement. Caustic had very little light inside, besides a small window and the lanterns he had been collecting.
The Wolf's eyes were almost good enough to see through the darkness, but Caustic wanted to watch this experiment in good lighting. His home had a privacy fence- dilapidated, but a fence none the less. It was wood, six feet tall, with various holes through it and boards missing. Caustic hung signs on the outward facing portions, notices not to trespass or disturb him. That way, it was their own fault if they were bothered what he did in his own backyard.
Caustic brought the cage out first, sitting it on a wood board outside. Inside the wire trap was a rabbit. He had fed it a few hours ago, and now it would serve its purpose as a test subject.
This kind of experiment was his calling. It was what he was known for, the desire to test on the living. Caustic considered it to be relaxing in comparison to his other, far more frustrating project. The portal maker had given him nothing but trouble, and Caustic was tempted to smash it. It was only way out of here, so he restrained himself.
He brought out the syringe next, held delicately in his teeth, and the voice recorder around his neck. Since the discovery of his own venomous properties, Caustic died to test it. It had some amount of a numbing effect, when administered in small doses. Octavio had suffered a bite from Caustic, and was numbed for hours. To note, Octavio's cheetah form weighed around 35kg. This rabbit should be around two kilograms, but Caustic lacked the equipment to test it.
Caustic placed the syringe down, watching the sickly green fluid inside move. He lifted his voice recorder, pressing down on the red button with a paw. "By my estimate, it is the second week of March, 2020. Of note, I have been here 52 days. I thought I would have escaped sooner, but alas." He sighed deeply, a green puff of smoke leaving him. "My," he coughed, "Overall health has stagnated but is expected to decline. This is my second experiment in this dimension, where I test the properties of my venom on a rabbit, dubbed Test Subject Five." Caustic grabbed the syringe, carefully, in his left paw. He sat back on his haunches, holding the recorder in his right. He had made grips for both objects using clay, but it was annoying. He wanted hands.
"Five, weighing approximately two kilograms, will be administered point two-five cee-cees of my own venom, and I will observe its affects. The syringe will be administered now." He let the recorder fall out of his paw, ceasing the recording. He opened the top of the cage, forcing his paw down on the small of the rabbit's back, implanting the needle in its side, pushing down on the plunger, then shaking the fur to move the venom around. He pulled the syringe out, quickly shutting the cage. He placed the syringe down, relifting the voice recorder.
"The venom has been," he coughed, "administered. Will update as items of note become clear. Test Subject Five is extremely stressed, otherwise. This may affect the results."

Caustic is mumbling in his recorder, watching the rabbit. The scientist is transfixed by his experiment, and Caustic’s mind idly wanders to his beautiful gas. It was his magnum opus in every right, and the wolf’s chest puffed as he thought of how he had fallen in love with his own creation.
Results would not leave him. Results would not go cold in his hands. Results were attainable, controllable, and experiment with an end goal in mind.
There was a beauty to death, Caustic knew. The beauty could be interpreted in many ways, however. Luc’s body in his hands was ugly, but Octavio’s open chest was beautiful. Maybe, killing Dr. Humbert and joining the games left Caustic desensitized.
Luc would probably be horrified by what Alexander had become, he idly thinks, looking up at his fence, then back to the rabbit.
Death was a constant variable and experience in the games. While he had rightfully earned his title as an Apex Legend, he was prone to mistakes and being outwitted or outgunned, just like everyone else.
A mistake was what brought him here.
Caustic raises the recorder to his mouth, shifting as he observes his experiment. The rabbit laid on it’s side now, eyes closed as the venom took its hold. ”Subject seems to be sedated, but alive,” he notes. Perhaps a higher dosage would result death in the succeeding tests? Fascinating. Caustic's former NOX gas had many qualities, it was suffocating and corrosive, and spewed in horizontal green clouds. Nothing interesting to the viewer, but to Caustic? It curled into intricate green clouds around his test subjects, snaking into their lungs and killing them from the inside out.
Caustic could have made stronger gases, easily, but the syndicate always held him back. The games had to be "fair" and "balanced" that way. The wolf's ears laid back as the child approaches, the one with the bird, and his eyes narrow into a glare as it speaks. "No, you're not." The rabbit is his test subject, it was prey and it's duty was to die by Caustic's tests, and be subsequently eaten. "Even if you did, it is incapacitated. It cannot run away any longer." This was the one good thing about the Pitt, there were less people to bother him, and less people to meddle in his morally-dubious privacy.

Caustic's cold and clearly annoyed gaze turns to Aurum now, his tail lowering in defense. He had to do whatever this one told him to, he knew. He could already guess the words forming in the proxy's mind, about his moral corruptness and that the rabbit would need to be killed or set free immediately.
Caustic's methods were only controversial to those who lacked imagination. So, of his options, he elects the easy one: lying. His face remains the same expression, clear annoyance and defensive about his work.
"I have learned I possess abilities previously unknown to me." A half-truth. He was not going to mention what the ability was until asked to explain. "I am a scientist, Aurum, so I must test the world around me in order to understand it. It is my civic duty." A lie, these experiments were for Caustic, truly. They kept him busy. "I am testing the properties of my ability. This way, I may use it in combat, and aid Tanglewood to my best ability."

Caustic's head tilts to the left as he watches a shudder run through Ivan. Idly, he wonders if that is fear, and his ears perk upwards at the idea. Green eyes flicker to his test subject, making note of it's labored, slow breaths. There were things Caustic understood to be true that the members of Tanglewood could not- first, this was the natural order of the universe. If the rabbit was willing to survive, it would be in Caustic's cage. Second, the strong would filter out the weak, as the wolf proved himself to be the superior combatant by hunting down the rabbit. Third, Caustic's methods were only controversial to those who lacked imagination.
If this was not the natural order of the universe, the rabbit would have never ended up in his grasp, and it would not be suffering now. This rabbit's purpose, as a member unable to function in the clans, and as far as he was concerned, equivalent to an insect. It's life was inert, meaningless, but it could serve purpose in Caustic's grand experiment. 
To suffer for another...
His eyes glaze over for a brief moment, thinking of Octavio's body. Octavio enjoyed suffering at Caustic's expense, so to proclaim such a thing as wrong... was incorrect. The dot about Caustic's left eye pulls up, his face attempting to morph into raising an eyebrow as the child spoke.
He watched Ivan look towards Aurum for support, and Caustic's ears tilt back again.
Oh, he's done for.
"Dr. Caustic," he interjects immediately. They were not friends, Aurum was not close enough to the scientist to drop the Dr. from his name. Caustic's face furrows, puffing out his chest, raising his tail and letting his ears perk. Caustic is, unknowingly, displaying dominant behavior. The Wolf's mind is trying to compromise and mix with his human intellect. He waits for the Tigon to finish, lips twitching, but he attempts to reserve himself.
It is not a waste! He wants to scream at the proxy. Caustic's experiments were vital and important, this rabbit was serving it's purpose, and when it died, he would eat it. Was Aurum so foolish to think the scientist would waste anything? Evidently so! His ears tilt back again, fur raising and bristling, be he knew he would have to do as Aurum said, and he seethes at the seams at the idea. He opens the rabbits cage from the top, snaking his arm inside and finding the creature's throat, pressing down on it.
It would die, soon, cleanly. Caustic knew he would have to contend with ripping into it with his teeth later. His head tilts back to give Aurum a sideeyed, narrowed gaze. "Are you so ignorant? Waiting until an actual battle to test my abilities is foolish. I could not perform to the best of my abilities if I waited." He begins to doubt the tigon's intelligence, "Does a blacksmith wait until war to test his new sword? Never, Caustic had tested his traps hundreds of times before he used them in the field, to ensure they were durable, expelling the same amount of gas as the same speed and duration every time. Testing was vital to the process. He twists, feeling the rabbit give a death's gasp under his paw. He closes the cage, grumbling as the Wolf's brain is already forming mental images of ripping into it.
"It has perished, and I will eat it. Could you please expel yourselves from my property now?"