Design of characters from the phone game "Puzzle&Dragons"

Following is a story I imagined while I drew this picture~

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"One day I will surpass Satan, becoming the strongest demon!"
The kid says proudly.
Finally,he gets the mysterious power accidentally...
"Yes...!I feel I get stronger!my dream will come true!"He grows to twice the height of his companions,but it seems not easy to stop...
"Buddy?Are you OK?"
"More...more!Give me more!"His rumbling voice.
His body continues to swell and start to transform!He evolved into a higher level of demons!
Now he's almost 10 ft tall now!The same height as Satan!
His buddies could not help but get excited to see this scene."You did it buddy!Look at you!You are so huge!"
"Not...enough...more!I want more powerrrr!"His body still trembling and began to glow,that kind of force seems not to dissipate...
"Rooooar!!!"After the demon's roar,his muscles began to bulge and rip his armor.
"I am no longer a little devil!HAHAHA!"He growling in laughter.
Even the earth trembling with his deep voice,He's size and ambitions grows bigger and bigger!
"Oh my...he becomes...a giant..."His buddies are totally stunned.
His growth seems finally over, for the time being so...
"Yeah...It’s time to find someone to prove my strength..."
Now,an almost 20 feet tall monster smiled grimly,intend to do something...and he knows,no one can stop him...

Thanks for reading!