in my initial response to the thing coming into Heph system, I sent the test room back to it's universe, leaving a severed piece of the elder god growing in this universe, it was, as of last turn, the mass of a small planetoid. In the same turn that I sent the room back, I ordered all weapons fired at the thing. PW didn't elaborate on the effect this had.
Edit: of course, he may have not included any orbital or Heph mounted systems, and considered only the weapons on the warship I am currently on, so there's that.
I'd add a small clause to have some/all conventional weaponry open fire on it again for this turn, just to ensure pw didn't just miss it and so w can confirm what, if any, effects it will have.
Also, you could check over how big a front it is moving. Does it move as a whole, like a blob, or does it have a smaller 'leading edge'? If the latter, you might have some options.
Oh, and remember that trick with the pocket dimension portals? One thing you could also try is to create a dimension with absolutely ridiculous gravity (maybe not black hole, but close enough) and open up portals to near where this thing is. If it is affected by gravity at all, it should get sucked in once close enough to the portal (so be sure to open a few portals at point blank range). You could also try things other than gravity of course, you can change the parameters of the pocket dimensions quite a bit (eg make the pocket dimension hotter than a sun and open a portal to use it as an impromptu heat cannon).