A man wakes up in his armchair one day to find a horrifying guest waiting for him in the form of a tall, lean, lumbering solid shadow with an old crt tv for a head. He's terrified as heck of the creature and nearly has a heart attack when it starts "speaking" to him. Contrary to the angry white noise flitting across the screen, the being's voice rings clear and tranquil, almost soothingly, almost reassuringly. There was nothing for him to do but to listen to the loud whispers the thing filled the dark still air and listen he did to these instructions:
"Awaken messenger. You have outlived the time for slumber. Duty bids you to act as mine prophet. Catastrophe awaits your kin and you will deliver mine tidings. Many souls will come undone and rot shall erupt from their husks. Such is the sign of foulness awakening, such is the birth of its warring soldiers. In time, soldiers will conquer the lands and the seas forever more. This realm welcomes none who remain past its new master. Heed mine aid, take to the sky and to the lonesome white. Shelter hides beneath its facade and mine truest vessel lays slumbering. Awaken your master else your kin shall be soldiers entirely, eternally. Deliver mine bidding messenger and assemble the waking. The cycle must begin anew."
The being pulls the man in an instant deathly tight embrace and vanishes as soon it touches him. A mark has been left in his eye and arm and the man finds himself now able to see and hold the unseen that reality hides from them. Catastrophe is coming and he is the prophet to herald it.
This was more a sudden writing exercise for a cosmic horror story than a pitch. The rundown would be that the world is on the verge on being overrun by an elder being and the only salvation is for the protagonist to use his new eldritch sight and touch to bring together a cult that'd take him to the moon. He'd be able to weaponize the limit of a soul and deliberate rupture it to use chaos magic. It'd end on the world about to be swallowed by the rot and the MC just witnessing the grandeur of his master's awakening as he dies.