It was the first thing I thought of when I saw your mods come out - OMG we're getting a 'Riddick' mod and we've landed on M6-117.
Think you could make the darkness mod trigger every 22 game years, starting from a random number generated on landing? Say one time you land, it is, call it, 7 years till event, while another new colony would give you a different time to event?
That event would call on your other mod to unleash the critters, which would then wreak havoc for a while?