Warning: unmarked spoilers.
Efrain acquired the Von Viltheim powers due to his indirect link with them
In the second game, it's never explicitly explained how Efrain got those powers; even Death, upon encountering him at the beginning, sounds surprised by that. However, we later learn the story of Anna Von Viltheim; had her marriage with a Lecarde happened, Efrain and the Von Viltheims would have even been related. Still, that bit of shared history between their families allowed for a spiritual link; Efrain didn't even realize that he hadn't vanquished the evil spirits of the Von Viltheims, but rather purified them. They probably started manifesting themselves in their benign form to him, some time after the events of the first game.
Efrain's ancestor involuntarily caused the events of the first Lecarde Chronicles
We don't know if Anna Von Viltheim's fiancee from the Lecarde family was Efrain's great-grandfather (who then later married another woman), or some great-uncle of him; what's certain is that his leaving Anna, possibly because he was too dedicated to his job as a Knight of the Church at the time, caused her desperation and eventual suicide.Now, we know from the game that she was buried in the Castle of Eternal Night. It was most probably not a coincidence: the Duke of Guillecourt at the time, knowing of her history, made her grave in his castle look as an act of generosity, while in truth he sealed her restless spirit there, using her eternal desperation to gain power and, over time, poison the minds of her relatives to be converted to the cause of Lucifer. Within two or three generations, the Von Viltheims had become the ones we know from the first game.
The Church specifically sent Efrain to Austria and France
Related to the above. Efrain's superiors had knowledge of the events surrounding his ancestor and Anna Von Viltheim and, over time, deduced the link between them and the Von Viltheims in Austria. They sent Efrain not only because he was their best warrior but also because they believed he, as a relative of the man who inadvertedly caused all, had the duty to right the wrongs of his ancestor, and remove a stain from his own family (even if he didn't know of it himself).A few years later, when reports of supernatural events started pouring from the same region of France where Anna was known to have died, they knew Efrain was again the right man to send, so he could finish the job he started in Austria.
The Corpse Guest was born from a Poltergeist fusing with the hatred and resentment of the spirits of people operated upon in Guernon University's operating theater
It is doubtful that the Poltergeist and the Corpse Guest are different kinds of spirits, as they share a similar form... Both of them look like a skull. Furthermore, it can't be a
coincidence that both of their themes share the word "Guest" in their names.This would nicely explain why the Poltergeist encountered in the university's attic disappears after throwing a total of nine objects, yet the Corpse Guest has to be beaten: the Corpse Guest is sustaining itself with the hatred of those spirits... Which makes one wonder:
what was going on at Guernon University?- Considering that the benefactor of the university, Jean d'Albaret, was probably Constance's father or grandfather, and that the evilness of the noble families of the Duchy of Guillecourt dates back at least a couple generations, it's very likely that Jean had made the university a place of unethical experiments.
Anna made a deal with Lucifer as well as the rest of her family, and she is Katharina's daughter/sister.
Let's look at a couple of facts: Anna is practically unbeatable without
all five Von Viltheim equipment, is found in a very secluded area of the Garden of the Dead that you can't get access to unless you can go through mirrors to get the required object. Heck, you also can only get some of the equipment from the departed Viltheims. Why does she have so much protection, and why would the Viltheims be willing to let you kill their relative?
The idea goes like this. When the other Von Viltheims were making their deals with Lucifer, Anna wanted a more innocent desire fulfilled: She wanted someone who would love her and that she could spend the rest of her life with. Lucifer, being incapable of granting a wish for true love instead tried to play matchmaker and set up events so she'd meet someone with good compatibility. Efrain's ancestor Lecarde comes into the picture through this, Anna's happy and everything is going well up until the Wedding Day.
Now for some reason, this Ancestor finds out the true nature of Anna's family. Maybe he witnessed what they do in their halls. Maybe he was told by Anna, who wished to come clean. Regardless of the truth, this ancestor is repulsed and flees, leaving Anna alone and in despair. It's probably here that Anna realizes her mistake. She essentially sold her soul for something Lucifer could not grant, and will spend eternity in Hell. Feeling that she has nowhere left to go, she goes to France and commits suicide.
The family you face in the first game decided to arrange things so that Anna would not go to Hell. They took her body to the Castle of Eternal Night and created the section within the Garden of the Dead so she could rest peacefully without being disturbed by any of the cultists. Friedrich, whose abilities allow him to enter mirrors, hid the Cup of Untruth behind a mirror so that people could not even get to it without either him or the Silver Wand which was also hidden. Liese may have helped set up the tomb, Katharina enchanted Anna's body so that nothing but the Von Viltheim Equipment can actually hurt her, and Leopold set up the constant storm of zombie bridesmaids to kill intruders. Gerof took the sword with him, and Wilhelm could've scattered the rest of the equipment (and possibly the Silver Wand too) throughout the castle proper.
This now brings up the question of "why is she still beatable in game"? Maybe the Von Viltheims left some things around so that, if Anna could be absolved in some way, they could kill her themselves. Another idea is perhaps they wanted a Lecarde to stumble upon the place, if only to get massacred by Anna as a bloody form of karmic vengeance. Given that you do get some useful equipment (the Von Viltheim Sword among them) from their remaining spirits, perhaps they realized that being killed by Efrain absolved them of their sins, and want him to kill Anna so she can finally, truly rest in peace. This may also explain why they're using their now holy powers for Efrain and how Anna simply goes back to her altar, maybe sobbing in relief because she can finally rest in peace.
