Kingdom_Of_Hearts wrote...
Any ideas on a creature being only killed by a certain weapon?
Well its not so hard to do BUT its a bit nonsense actually. Spellcasters do not use weapon, so what about them?
Also, do you want the creature to be damaged by other weapon or not even that?
The best solution is OnHit unique power with tag based scripting where you perform saving throw vs death. This still leaves the possibility to kill the creature by other weapon or spells, just not so easily.