I would like to create a collision plane that only effects player characters and never hinders NPCS.

I have tried selectively removing certain collision layers but the plane still blocks NPCs (but not the player) with no collision layers included. This is what is boggling my mind. If there are no collision layers, what are the NPCs contacting?

I would like this plane to work even if the player is nearby. E.g. the player and an NPC are side-by-side and both try to cross the plane, only the player is blocked. This means that enabling the plane with a trigger when the player is near would NOT work.

Thanks for your help everyone!