I'm trying to use Lua to record how many actors one of mine has killed within a certain time frame. What function or variable do I need for it to detect enemy deaths within a certain time span?
Basically if one of my actors kills 2 actors within 5 seconds of each other, It should report a Double Kill,
if he kills 3 within 5 seconds of each other, a multi-kill is reported...etc.

This will be really hard to get to work properly. You could try tracking any particles that are headed away from your actor and checking if there's any dying actors close to where they were in the last sim update, but that's not very feasible.

You can do it in a custom scene, since isactor checks will work, but destroy functions run through a scene also work. Unfortunately, that requires custom scripts on ALL actors involved.

And if you just have destroy functions on actors outside the scene, when they die it'll crash CC.