Blackbot |
Interesting question. I could see both arguments:
1. No, that wouldn't do the trick. The statblock given for the possessed NPC mentions nowhere that he is undead, thus he's not affected by positive energy. His body "shields" the vilkacis within. Note how the vulnerability to silver specifically mentions that the possessed creature too gets dealt the bonus damage, implying that most things affecting the vilkacis do not affect the creature possessed.
2. Yes, because the energy goes "through" the body and attempts to attack the vilkacis within.
I probably would not allow it in my campaign because I feel like possession should be more difficult to overcome than just blasting cure moderate wounds, lay on hands and channel energy onto the possessed person. So just do what you feel appropriate. I feel like it is a great way for the players to get creative and not just fire everything they got. In our group the paladin immediatly critted the possessed person with his hammer (x3 damage) and splattered his brain across the floor. That guy will have some nightmares once they figure out how easy it is to overcome the possession...