Jason was successful in taking over Frederick's body. Due to whatever witchcraft was casted onto them, Frederick's skin and flesh molded to copy Jason's physical appearance.
Except for his ghastly face, his height, broad shoulders, slender fingers, his stature.
It was like Jason has come back to life.
Seeing him, Lucia was extremely delighted. She hugged him and buried her face against his chest.
The priest and the two nuns were exhilarated seeing this scene.
They have successfully accomplished their mission. The god they worshipped guided them to that woman's house that night. Saying one of their god's holy object was with a woman and in the man's neck.
Their god informed them to grant whatever wishes the woman who has the object has. If she really wanted to kill people and resurrect someone from the dead, they must obliged.