How to make an NPC perfectly neutral?

[PAPVAFS11]

For some time, I've been trying to make a character completely neutral and/or undetectable to all other NPCs. This is essential as the NPC in question is intended to serve as a mobile environmental obstacle that sometimes spawns in place of creatures.

 

However, I have no information on how to do this. Setting the character to an invulnerable ghost in its base flags still allows other NPCs to detect and attack it. Is there any way to accomplish this?

[McclaudEagle]

The only thing I can think of is to just add every faction you expect the NPC to come across to the character, and set them all to Neutral. That should at least mean the NPC can move around in peace; it shouldn't attack or be attacked if you do this. However, I've never tested this, so I can't guarantee the results.

[RoyBatterian]

Create a new faction for the NPC, then add the other factions to it as allies. Should then never be attacked by any other faction.

[PAPVAFS11]

I'd hoped for a more elegant solution, but I can make due with this. I'm sick of not including this concept in the game. My appreciation goes to the both of you for the assistance.