A fun concept, presented in an actualizable manner. The mirror universe is evocatively depicted and the big martial threat is both creative and horrifying.

My two gripes are that the writeup is presented in long, wide paragraphs which make it a bit harder to pull information from than is strictly necessary, and that I didn't see anything in the mirror universe that would tell me as a player "Alright, mission complete, go exfil." I think I'd be inclined to continue deeper in if I got as far as the Radio Wraith, and there's not quite enough here to support long term expeditionary play ala A Red And Pleasant Land or such. 

Worth getting, for sure. The FIST community is better off for this existing. I'd print it out and hit it with a few highlighters, or make cheat sheets, before bringing it to the table though.

Very solid one-shot mission with options to add more details depending on the playstyle of your gaming crew. The scenario includes noteworthy characters and a cool creature, as well as descriptive language that helps set the scene for key encounters (e.g., meeting the informant, discovering the blood trail in the Shadowside). The Radio Wraith should make for a unique and challenging boss fight. Plus, there are options presented at the end for extending this adventure into something longer (e.g., finding a cure for an otherworldly infection that’s slowly turning you into gold).

A few minor points: I think there may be a typo with one NPC referred to by two names (Goat & Crow). And I recommend tweaking the wording of the Opera House encounter to be clear that the soap smells foreign made, rather than potentially implying the locals don’t wash. Alternatively, this could be changed to highlight the smell of their equipment (e.g., gunpowder and grease that doesn’t fit with the Opera House aesthetic).