The following scenario happened in an old game; The DM already made a ruling on the issue, which is fine - but I was curious how the "willing creature" aspect of the protection from evil and good spell works if the creature is already possessed.
In that game, we encountered a possessed child. I tried to cast protection from evil and good on the child so that they could fight the possession by having advantage on any new saving throw against that effect. However, the spell says it must be cast on a "willing creature".
If they are already possessed, obviously the spirit won't agree to the protection from evil and good spell being cast on them. So how can an already possessed individual get advantage on saves against possession?