The book of Genesis tells of how God created the earth in six days, as well as the first humans. He created Adam and Eve in his image as pure and uncorrupted beings. However, Lucifer seduced and slept with Eve within the garden, unbeknownst to her husband, infecting the human race with original sin. Eve had two sons, Cain and Abel, with the latter being the son of Adam and the former being the son of Satan. This led to God rejecting Cain and embracing Abel, leading to jealous rivalries between the two which would culminate in the first murder. Adam and Eve would go on to have another son named Seth, while Cain was branded a murderer and forced to walk the earth alone. Therefore, while the elves of the world stem from the seed of Seth as pure and uncorrupted, the human race would stem from the seed of Cain, tainted with the stain of original sin that he had passed down from his mother. This was all part of Satan's grand scheme to screw over God's divine plan by making humans susceptible to his manipulations.
Through the taint of original sin, Satan has created for himself a backdoor within humanity, allowing him to walk the earth once more. This taint has been passed down through the human race for thousands of years and would culminate with a mortal who would bear the anti-christ, Satan in human form. A team of exorcists working for the Inquisition has located the soon-to-be mother that the Devil has chosen and has taken them into custody. As the mortal goes into labor, the team would perform a sealing ritual which would postpone the birth of Satan into the mortal plane. This status quo has continued for years, with the devil attempting to break the seal binding him to his realm, and the exorcists performing the ritual. Through this method, the catholic church has continued to trap Satan in hell.
However, the method is taxing to the vessel, inflicting physical and mental stress. The years of this ritual being repeatedly performed has weakend the mortal, ultimately leading to their death. This proved to be a mistake, as it caused Satan to manifest in physical form. It turned out that Satan was able to cross over into the mortal world regardless of whether the vessel survived or not. However, while the anti-christ was able to achieve his goal, he is only at half strength. The breaking of the seal by those other than himself has somehow weakened him, preventing him from manifesting his true power. How would this be the case?