Self Destruction

Inspired by a cartoon I grew up with as a kid. A character unknowingly gave a demon access to our world who uses their powers and the body of the person to try to bring about an apocalypse

Sitting alone I listen to whispers of the Ancient Powers. They once ruled the world and one nearly destroyed it 
It is him I listen for.
Mortal, hear this plea for help. Revive me in your world so that I may exist in both. Now is the time to claim my belongings. The reward is your every desire made real. This is the Destroyer: be my servant and give me your body as a pawn to my reign. 
Gracious Destroyer, show me your world of chaos. Your home of fury and hell sits defiantly in my soul. Infect and grow using our collected thoughts of destruction. They are the key. 
I am the portal allowing you passage to this mortal dimension. Promise me passage back to where you came and I shall give you my body to claim what is rightfully yours. 
I allow you to reach my domain. If passage you give me, then passage I give you. Soon my possessions will be mine, ownership will be claimed over what was wrongfully taken. Our joined hatred of innocence will bring me back, bring us back, to full power. 
I am here - Let it be undone. 
Undone. Unleash your power, terrorising the people and the planet. No mortal dwelling shall have any breath left to stand. The sweet music reaching our ears will be that of screams and collapsing buildings: Observe the sweet revenge we have wrought. As it slowly burns we shall return to watch from our heaven as we enrobe ourselves in total annihilation. 
Foolish human. I will return solitary to my domain. You are forever bound to this realm and will burn with grief as it burns to the sounds of death you conducted. 
We are joined. You cannot leave me here silent and unnoticed. I forbid your lies to dissolve into my skin, to dissolve into reality and be made real. Our link was prohesised; even if I stay my soul will always be with you
Chain your complaints to your mind and stop them wandering. I promised nothing. I am all, I am power, I am free.
Power is never free, Power is controlled by greed and you are bound by your controller. 
I thought to cleanse, to purify was your aim, to reclaim that which was lost. You are a false Ancient. I refuse to be bound to one as weak as mortality. 
Cut our connection and existence will flee you as well as I. It is in vain, my reign is all
I slash at our join to end your dominion. It is done - the connection lost. 
We cease to exist. The Earth will grow again and forget your torture to be good and full of life once more.