Rallan wrote: Everyone's got the means to keep that sort of outbreak under control.
Given this statement, if I may say so, Rallan's universe is doomed to horrific chest-bursting destruction ( I mean that in the best possible way).
The biggest theme in the Alien movies is summed up in the phrase "Nuke it from orbit, it's the only way to be sure". All four movies have a running pattern of whenever anyone tries to 'control' these things, that's where the problem comes from. Ripley knows what to do, see an Alien, kill an Alien, no exceptions, no caveats.
The sub theme is that the efforts taken to 'control' and 'study' the infestations are the very things that let the beasties out to wreak their slimy brand of havok. Any beings in Phase World who think themselves invulnerable and who would want to 'study' or 'use' these things would be the ones who bring the horror down on everyone. Inglix would want a look, his efforts would bring them to UWW. Thraxus would *have* to see one (Of course all that phase world tech would be able to keep in caged... right?), and *BAM*, they're on phase world. CCW, they'd have at least one major laboratory facility which would become a bug hunt.
Naruni Enterprises? They'd want one for 'product research' purposes, there goes that facility.
The only race which would have no problem, The Intruders (they kill anything that's not them.... this is the right way to go for this threat).
The theme of the beasties is the ultimate Right-Wing villain. Do not study them, do not try to understand them, don't communicate, don't use any foolish notions of keeping the infestation 'under control', your very efforts to do that will lead to your demise.
Things to play with. Since these guys have this theme, the sub-theme is "Oh, but we learned from last time, it'll work this time! It'll...... AARRRGGHHH". So play with that in the Phase World milleu,
For example, unpleasant trick #1.....
Thraxus gives the party High end phase beamers (only the best!) for the purposes of them party bringing a corpse back. That should be good right?
Well, what if the Phase Beamers don't 'kill' these things, they only put them into a death-like coma..... no one realizes this... until their specimen wakes up and now the party has an infestation somewhere. Pick a place, make it messy.
Unpleasant trick #2.
Telepathic contact..... Doesn't give any information. Seems a total dud. However, unbeknowest to everyone else, it *does* have some sort of horrific effect on the telepath, like making them 'sympathetic''. The sort of being who will 'want' to be impregnated and who will sabotage containment facilities. Poor peacenik Noro, they got it coming.
Unpleasant trick #3
Ugglies can get anywhere. If an ugly gets impregnated, then the impregnated ugly can get anywhere. Ugglies could become a catalyst for this whole thing.