[Sichr]

Group I play with happened to have CQC with Nuclear Toxic Great Form spirit, with GM optional power Astral gateway...and Astral rift opened on site (cursed and haunted Winternight submarine base) When final confrontation took place, I found out that not only Astral gateway do not posess such threat to players as it shoudl, thresshold is just 3 to remain on this plane and "it is doable", but I found out that it is critical mistake for spirit to have this envinment as a battleground. No matter how strong Force 13 spirit it may appear, by the RAW: Every physical object affected by asstral gateway (thus everything inside Astral rift space) become dual. That means not only mundane players. It also means Vindicator and 500 Ex-Ex rounds and Battle/Sniper riffles become dual and as such there is no ITNW in play. First round of the combat was also the last one. Even GM (me) was "a bit" surprised. Watch out for it and don`t make such mistake yourselves

[TheNarrator]

I'm actually going to deliberately take advantage of that fact when I make my players fight a master shedim this weekend. They'll need their bullets to work to stop the onslaught of shadim coming through the rift. 

[Sichr]

Thats exatcly the side Ive used in that run

[TheNarrator]

To keep things from ending too quickly, however, I think I'll have the shedim put up a Physical Barrier spell beforehand. It knows that its ITNW and Regeneration won't work while it's using Astral Gateway, and it's smart enough to take precautions. That'll force the runners to deal with its shedim-possessed ghoul minions so that they can focus on cracking the barrier without distractions to have the boss battle, instead of just ganging up on the boss in the first Initiative Pass to wipe him out and ending things early. (Plus, it gives the new demolitionist PC a chance to ply his trade by rigging a charge on it.)

So thanks for bringing it up, since it made me think a little harder about villain strategy. 

[Mantis]

Ummm the Astral Gateway power opens an Astral Rift, which in this case should lead to the home plane of that toxic spirit. It is basically a way to bring the whole group along on an astral quest or do something like the Harlequins Back adventure. It doesn't let you just ignore ITNW on the material plane. So your party should have gone off to the toxic spirit's home meta plane and tried to fight it there. Not a nice prospect.

[TheNarrator]

... forcing all physical objects within the area to be dual natured...

Against dual-natured objects, ITNW wouldn't apply.