Having dragged Sven into the laboratory Serina proceeded to slam him down onto a hard table made from a magic steel with an ice attribute and his arms, legs and neck where strapped with magic steel cuffs with the fire attribute.
Screaming Sven was in pain and unsure of what happend as after seeing the laboratory his vision became blurred and he was staring at the roof. Afer a few seconds he started to scream in pain due to a constant cold on his back he could feel his body start to heal itself and he noticed an excruciating heat around his wrists neck and legs. He was in a constant state of hot and cold.
"Help mee! Please Gaia please save me or kill me i don't just don't let them torture me" Sven cried with snot and tears steaming down his face.
"Let's leave him to calm down before we start, have some one keep him fed we will proceed in 2 days" Serina commanded and everyone in the room left.
Over the next 2days Sven had given up on crying and also on getting out of the situation alive his body was taking so much damage that even as he healed his body would have extra energy left his healing wouldn't stop anytime soon. But at the same time he was stuck in a internal struggle of whether to waste his extra energy and attempt to break the shackles holding him or keep the energy to ensure he can heal from the damage done during the experiment.
Although at the end he decided to wait knowing that even if he did escape he wouldn't be able to beat everyone in the lab especially Serina. Finally through the torture Sven heard Serina and the lab workers come back he was somehow glad that his 2days of pain were now mostly over.
Serina came over to Sven and whispered in his ear "I'm not going to enjoy this but if you survive you will be a lot stronger than you currently are you will be a new stronger breed of human somthing surpassing nature, you will be the start of a legend.... probably"
Hearing this didn't ease Sven's already racing heart but instead made him even more scared and ofcourse the next words out of Serinas mouth just made him even more scared.
"Alright Steve grab the limpet core and Bob cut out the boys heart we have to do this quick or he will just grow it back" after saying this a short man with grey hair ran to one of the displays and grabbed a magic core and handed it to Bob a thin tall Woman with yellow hair.
While all this was happening Sven was still awake and could still feel everything happening to him he watched as Bob cut into his chest and cut out his heat before shoving the mana core into its place. He could feel the hole in his chest start to heal and could feel his heart regrow but other than the immense pain he could feel no other changes.
Serina went to inspect Sven and noticed he was still perfectly normal he wasn't stronger and hadn't mutated she confirmed this by using a status orb to read his stat page it was the same as before the experiment started.
Confused she ordered they do it again this time with a spirit fox core instead. The same procedure played out cutting out Sven's heart and replacing it with a mana core them letting him heal. Once this was done Serina once again checked Svens stats and was confused when again it hadn't changed.
Furious she screamed "for fuck sake if you two fuck wits can't do this properly next time I will do it myself after personally killing the both of you"
Hearing this and not knowing what else to do both Bob and Steve ran to the cabinet and grabbed the strongest core they currently had the core of a giant mutated waterbear somthing that was rare and almost impossible to kill they where sure that is this was the best chance at success they had.
With the core in hand they ran up to Sven and as they where about to implant it both of their heads where sent rolling across the floor. "What actual dick heads, they where going to use a core that I was saving for a special someone on you, they deserve to die" Serina said placing the waterbear core back where it belonged.
Turning around she walked to the opposite wall. "If some of our strongest cores don't work on you how about our weakest one?" She said grabbing a small core the size of a pingpong ball that had a brown hue to it. She walked up to Sven and punched him in the chest burying her hand in his chest before taking his heart out. Taking a step back she dropped the small core into the cavity she created and waited for Sven to heal.
Bit after 30second he was still not healing instead his body started to spasm and convulse as he started to foam at the mouth with blood coming from his eyes and ears. As this was all happening Serina started laughing "its working yes you may not become the strongest like I promised but you will still be better than you are now" she yelled while running to a desk and started writing down notes on the experiment and the outcome.
Watching Sven go through the process of mutating she would describe everything she say from the bleeding to watching as his arms and would rot away and regrow to how at one point it looked like all the bones in his body liquefied but after 3hours of Sven's body destroying itself and healing he finally stopped sprawled on the floor unconscious from the pain.
Upon closer look serina noticed Sven was now 5 and a half feet tall and he had no excess fat but now a body full of defined muscles in the short span of 3 hours he had completely changed from an over weight child to someone who was more healthy looking than most adults.
Serina used the status orb again and noticed while all his had changed she wasn't impressed by how little bug since he mutated from a weak core it couldn't be help, a 3poing increase to all stats was a huge bonus at low level but what really had her going was his race had changed from human and now read 'ኳҶኡ-ኳҶᘉᖊ ꔎኑᕂኳᖊ൩Ҷ'.
"Well Sven we successfully created a legend" Serina said to herself before reaching down to grab Sven and finally walking out of the room.