When Mark's fingernails dug into Sean's back, he knew something was terribly wrong. He arched his back in pain.  "Mark?!?" his voice quivered.

"I love it when you screech that way."

Sean was horrified when the voice that responded wasn't Mark's. It was leathery and deep, like a snake's would be. He tried to back away from the horrible thing that was using his boyfriend's body, but the it held him tightly.

"Now, now," Darkiplier, taking Sean's chin and shaking him roughly. "There'll be none of that. I thought Mark taught you better."

Sean's eyes widened in terror. Mark wasn't himself anymore. His hair was black completely now, and his skin was a pale shade of grey. The eyes that stared him down with cruel, murderous passion were bright red. "Mark?"  he managed, just barely. He seemed frozen with fear. "Where's M-Mark?"

Darkiplier bit his lip with teeth so razorlike they made his skin bleed. "Hm..." he glanced around the apartment, clucking his tongue as if he were a real estate agent assessing a dirty home. "Not too shabby. Different  than I remember, to say the least. Mark's really done well, hasn't he?"

The thing turned his blood red eyes on Sean, taking in every curve of his body in a way that made the Irishman incredibly uncomfortable. "U-uh," he stammered, looking down. He really tried to focus on the floor beneath him, desperately trying to come up with a logical conclusion. This thing, this thing isn't Mark, I know that. Then what is he? Maybe....he was interrupted by the Anti-Mark's (Anti-Mark? Sean thought as he pursed his lips. He'd have to think of a better name) large bulge. He couldn't help it, he just instinctively checked out the thing's package. In a rabbit trail of thought, he wondered if parasites could even have packages.

Darkiplier growled and forced Sean's chin upwards. "What the hell do you think you're looking at?"

The Irishman's eyes expanded to the size of dinner plates. He tried to hide the hint of lust he knew he was showing, but it was too late. The thing seemed to regain its composure. It smiled menacingly and gripped Sean like helpless prey in a rabid carnivore's jaws. He narrowed his eyes at the small green haired man, taking him in. Swallowing up his essence like it was a delectable meal.

"He's made you so, so weak, hasn't he? He's tied you up and thrown you in the closet," Dark scoffed. "He was always one to leave a man behind."

"Who?" Sean blurted, and instantly regretted it. Apparently, the thing didn't like being interrupted.

The Anti-Mark (God, Sean thought, that name was getting to him) pursed his lips, the spot of blood trickling down his chin. "You're strong, I can tell. You wouldn't fuck up an assignment like a bitch I knew. God, he was a complete ass. Couldn't do anything right." he grinned, and the Irishman noticed that his tone didn't match his words. The thing talked like he hated the bastard, but his maroon eyes sparkled with....love?

"W-w-who was this guy?" Sean spluttered. He hoped to get the thing talking so it would lose concentration. Maybe then he could make a break for it.

Surprisingly, Darkiplier was thrown off by the question. Usually his victims didn't retaliate with personal queries. Often times there was a whole lot of screaming and mutilating. The blood always stained his suit. 

 
"He....he was an old friend, that's all. Just..." Dark trailed off. He cleared his throat. "He was my partner in crime. What a fucker, that one. So hot headed and definitely a wildcard. Oh, our lead assassin couldn't even control him. Good times, good times." Dark felt his eyes getting misty. He wanted to say more, but he restrained himself. He'd already shared way too much with this half human, way more than he wanted to. Just get the job done, he chided himself.  This little flailing bag of bones is no different.

Sean sensed a change in the thing when it started discussing the mysterious friend. He sounded a lot like....Anti.  The person he described sounded so much like Anti that he knew it was true. Anti would sneak out while possessing him and join a covert kill group. The thought made him sick. "This man, h-h-he's killed a lot, then?"

Darkiplier laughed like a madman. "Oh god, way more than you could even imagine. He was second best in our class. I was first, of course."

Sean needed to get answers. But, he couldn't get them while in this form. He needed someone with more experience. Anti. He grimaced. He hated the thought of intentionally letting the parasite take control, but he had no other option. The thing was going to kill him unless he had a connection to his target. Just this once, Anti. Sean bargained. And only if you swear to save my life.

Antisepticeye's black matter wormed its way back into the closest part of his mind. 

  My pleasure.

Dark almost recoiled when he felt a significant rupture in the human's psyche. The change was almost instantaneous, like a sky full of silent firecrackers. He could feel the transformation happening, but it was like seeing it for the first time. Even though Dark had seen thousands of parasite manifestations, Antisepticeye's was probably the most sickening.

His eyes turned black like giant pools of ink with small, bright green irises. His skin tinted a light shade of the same green. His ears elongated until they were at least two inches long. As soon as Anti's conscience fully present, he smiled maniacally. "Hello, Darky,"  he bared his fangs, "It's been a while."