There's this firefly mod that I use to have that caused all the creatures to try and kill fireflies for some reason. I'm wondering how I could go about doing this for a mod I plan on working on. I tried looking at the firefly script but all there was to it was whether or not the firefly light would turn on or off a curtain time of day.

a sort of hack way of getting this to happen is to have the fireflies scripted to toggle to AIFollow or AIEscort, then the other creature will target it to kill if they have a high fight rating. otherwise, a much verbose way would be to give everything unique id's and script for getdetected every few seconds so it doesn't kill framerates.

Not quite the approach I'm looking for, on the firefly mod it was still under wanderer I'm fairy sure.

I've actually done this on a mod I ended up scrapping, but it does require the actors to have unique ID's. Do the detection routines, and then "startcombat " I don't believe startcombat will take a partial ID, but I'd have to refer to the scripting guide to be sure.

You might also ask on Fliggerty's site, but the answer may involve MWSE.

maybe somthing like this example
(EG: script placed on a predator (unique kaguoti), so it targets its prey (unique guar) when the player gets close enough)


begin i_could_kill_that_guar

if( getdistance player == 500 )
AI_my_kagouti->startcombat "AI_my_guar"
endif

end

something like that?
theres also one in "waterlife" by abot that causes slaughterfish to be predatory and attack other fish, which i would assume to work better than my simple one, but you may need permissions from him to use it.

Morrowind world is almost player centric. You can do (sort of) this just using AI packages.
Set a "predator" creature to attack player (AI Fight setting >= 82 ), set some "prey" creatures around to escort player
Example AI packages
1: Wander (Distance: 4000, Duration: 24, Time of Day: 7)
2: Escort (Target: player, Cell: NONE, Duration: 0)
You can also do the same using equivalent script commands so you can test for conditions.
For other details and examples, you could see for instance Trevor Demented's http://www.tesnexus.com/downloads/file.php?id=1336 for AI packages samples on NPC, http://planetelderscrolls.gamespy.com/View.php?view=mods.detail&id=258 for AI packages/scripts samples ON creatures.