Creating plug in for AI?

I want to test some AI logic.

I’m a beginner with UE4. Is there a way to create a plugin that will affect the actions of an NPC?

What I envision:
I have game scenario ‘X’ to load.
Let’s say it’s the scene from LOTR where the 9 members of the Fellowship run out of Balin’s tomb into the great hall in the Mines of Moria trying to reach the Bridge of Khazad-dûm.
Ok, in that scenario ‘X’, I need to load the following NPCs:

  • dead Dwarfs
  • dead Cave Troll
  • dead Goblins
  • live Goblins that run drown from the ceiling
  • live Goblins that run up from cracks in the floor
  • all 9 members of the Fellowship (dwarf, elf, humans, mithrandirian, hobbits)
  • One fiery Balrog of Morgoth

I want each controlled by it’s own NPC logic from a ‘plugin’ (??) that I build and link to the game. (again ??)

If you can send me links to posts, or other articles on how to create NPC AI logic ‘plugins’ it would be appreciated.

How do I create these plugins - or libraries to control NPC’s?