The main difference between this book and other Big Event books like Bug City or Portfolio of a Dragon: Dunkelzahn's Secrets is that those previous books had One Big Thing that they were all about, with alternate campaign models branching off from the Big Thing's natural consequences (insect spirit's overwhelming Chicago or an implausibly rich dragon giving away 1% of his shit, respectively), but Year of the Comet is a complete grab-bag. None of the chapters have anything to do with each other, and only the first has anything to do with the titular comet.
I mean, technically you could say that SURGE - Sudden Recessive Genetic Expression - was caused by the comet. The book is actually a little cagey about it, but it started shortly after Hailey's Comet became visible to the naked eye and it ended shortly after Hailey's Comet was no longer visible to the naked eye, so it's at worst a very strong correlation. However, there's not really anything thematic that connects people suddenly gaining random animal features with the reappearance of a short-period comet. Why is that canonically popular pornstar a horny catgirl? Because of Hailey's Comet, obviously. Comets do that to people, you know.
It's one of those frustrating things about this particular era of metaplot-driven supplement-heavy rpgs - they were eager to tell us events that happened without actually resolving any of the most obvious questions. It's like they imagine that every GM's favorite part of the game is giving volatile non-canon answers to canon mysteries. "We'll never come out and directly say that the Sixth World's rising mana level will lead to an ever-escalating power creep and the introduction of countless new enemies, treasures, and character options so that you can give your players any explanation you like for the Comet-adjacent weirdness. But if your homebrew explanation is anything other 'the comet was an unstable preview of a higher mana level' you're going to have a hard time explaining future metaplot events."
To wit: is it actually the fun kind of ambiguity to hedge on whether possession of the Coin of Luck is responsible for Sharon Chaing-Wu giving birth to quintuplets? I guess "the mysterious artifact bequeathed to our family in a dragon's will was a placebo, it doesn't really do anything, and the quintuplets are just a coincidence" is a kind of worldbuilding. But let's be real. It was the coin. I think the main source of the ambiguity hear is the line's overall reluctance to make magical items that do things. For the most part (with no counterexamples that immediately spring to mind, at least) Shadowrun's magic items are more like equipment for magic-using characters. They add dice to or reduce drain from spellcasting or they allow magically active characters to roll extra dice while using an enchanted weapon. If one of these items fell into the hands of a mundane, it would be nothing more than a ridiculously expensive paperweight.
What this means, in practice is that something that seems like it should be powerful, mysterious, and valuable is just a macguffin. Yeah, someone will probably hire the shadowrunners to steal the thing, and then some third party will try and swoop in and steal the score, in true heist-movie fashion, but the stakes are basically "we have to move the Thing from one Place to Another!" Even as short out-of-character blurb "whosoever possesses the Coin of Luck will experience the blessings of enhanced fertility, both in their immediate family and their agricultural property. The exact details of this blessing are beyond the scope of these rules, but in the hands of a megacorporate CEO, it can mean billions in revenue" would have helped a lot.
Not that the Coin of Luck played much of a role in this book. It's just indicative of an overall attitude. The strangest manifestation of this is the way the Shadowland commentors will skeptically dismiss an event as being beyond the known limits of magic. For example, when Badr al Din ibn Eisa appears to come back from the dead (something we readers know to be possible in this universe, assuming Earthdawn is canon) most everyone just assumes he faked his death somehow. The idea that someone could come back from the dead is absurd to them. From my perspective, it's one thing for the characters to not be overly credulous and just automatically believe everything they here, but . . . where are they getting this certainty from? The reappearance of magic happened within living memory, so why are those people so sure the universe has no more surprises for them?
I suppose that's what the theme of Year of the Comet was supposed to be - you think you know what possible, but here's a bunch of unexplainable shit to keep you awake at night - but half the book was about relatively mundane politics (Ghostwalker going kaiju on Denver notwithstanding, though even that settled down into mundane politics relatively quickly) and except for the continuing presence of the Sheddim (spirits who take possession of corpses, though they aren't related to ghosts at all as far as I could tell) the magical stuff goes away with the comet. The book mostly just feels like "Stuff that happened in 2061."
Which is fine. I liked reading about the stuff. It's just, when the introduction promised me "a pressurized can of whoopass" I was expecting an event whose fallout would take decades to unravel. I suppose the new child emperor of Japan technically qualifies, but I'd have preferred for SURGE and the natural orichalcum to be permanent changes to the status quo. Or, failing that, for the presence of the comet to do something wild like temporarily step up Earth's mana level to something centuries or millennia farther along in the cycle. Give those Earthdawn survivors six months to reactivate their thread weapons and use their circle 12+ spells.
But maybe that would have been too esoteric for those fans of Shadowrun who were unaware of the Earthdawn connections (aw hell, let's face it - I was proposing it purely for an audience of 1). I guess I'm just going to have to count Year of the Comet as decent, but not quite as iconic as some of FASA's previous attempt at big metaplot events.
Ukss Contribution: Night mantas. They're manta-like creatures who float in the sky and occasionally stab people with their poisonous stingers. I like them because they create this spooky and ethereal imagery, but then they'll just attack like a normal animal. That's an interesting juxtaposition.