What happened to Paul de Pointe du Lac?
It has been said that Demons and evil in general tend to prey on the innocent and pure of heart; the weak. These people are often what are seen as 'perfect vessels' because they are easy to manipulate once acquired -- a second skin, so to speak. However, in some instances, they are not so easily acquired. Religion has often played a role in protecting those that are seen as 'weak' by forces of evil. In most cases this is usually by some Holy relic.
Paul de Pointe du Lac was a very religious boy, with aspirations to become a person of great importance within his religion. However, by now we are all well aware of what happened to Paul. But, why did it happen? What if Paul was being protected by a Holy relic -- unbeknownst to him? I believe in Paul's case, it would have been something simple, like a cross that had been blessed. Something he probably would have never taken off. But, perhaps, he had taken it off because he had felt his cross would better serve someone he felt was falling into sin. Someone, let's say, like his brother Louis. What if Paul gave his cross to Louis to protect his brother, but in doing so it left him vulnerable and ultimately caused him to become a victim to the Devil?
We know what happened between Louis and Paul was merely an argument, that Louis had never touched Paul despite his family's accusations. Even the servants had pointed out that Paul had looked up as though he had seen something. What if it had been an evil force? Or even Memnoch himself?
-- And Memnoch would have a reason for this, because Paul's death is what made Louis open to Lestat, and Louis being with Lestat was a catalyst for a lot with Lestat. [words from merciful-death] --
Further, this 'demonic' possession and/or influence in his life after losing his protection probably led him into a life of sin (which was probably something Paul was likely oblivious to). It would explain his skipping meals, his spending hours awake in his oratory with his arms outstretched like Jesus was on the cross, the hallucinations. His obsessions and pacing and attempting to coax Louis into selling their land and houses to acquire money... All of these things can be accredited to opium -- a popular drug of that time. Perhaps Paul had fallen into sin after losing the protection his cross had provided him and Louis actually had reason to be disappointed like he had felt at that time.