Marvin kept going, hearing the whistle but easily ignoring it. They were laser focused on their target at the moment, shooting out one spell after another. Whatever was sealed away inside of them seemed to like the sudden constant flow of dark energy and it began to fuel Marvin even more, that darkness seamlessly being transferred into energy that the mage could use outwardly. And while that seemed great for a bit, it came with a heavy price. It started with just a little trickle - something that Marvin could easily control - but it soon began to increase.
"I feel fine, I could keep going," Marvin replied as they shot off another spell.
However, as that little trickle increased, so did the dark energy. It was increasing at a speed that Marvin could no longer keep a hold of and it was starting to show now. The skin under the mage's clothes was turning darker and something suddenly felt incredibly off, causing a pause in their movements. It continued to creep up, eventually crawling up Marvin's neck as his emotions seemed to turn to anger, a craving for violence overtaking his senses.
"W-Wait... no no... no.." the mage stammered, feeling the dark energy continued to spread through him. It was like it was being pushed through his body without him wanting it to, increasing to levels he couldn't bring down.
A thick, heavy turquoise mist began to roll off of Marvin's body and onto the ground, pooling at his feet. The black and leathery textured skin continued to spread and Marvin's mind became hazy, having the overwhelming urge to just hurt someone.
"S-Stop... I-I don't want this..." the magician nearly growled, voice dropping to a beastly level. He fell to his knees, nails beginning to elongate into claws and teeth growing sharper.
Ugear was suddenly incredibly alert, feeling the levels of dark magic rising rapidly and beginning to worry for both Marvin and Jen. He stepped a little bit closer to Marvin, ready to step in at any second but also keeping an eye on Jen, silently asking her how she was doing with a quick glance.
"Focus, Marvin. Remember who's in control. It is your power, not anyone else's, you hear me?" the demon spoke firmly, wanting to make sure he was heard. These were words he had used before, but they just so happened to be used on another demon who also occasionally struggled with control.