Admittedly, I didn't plan it that way — a death-god appearing in the mortal world and leading an invasion force of a major city was just a plot hook for my core, high-level group, not something in which I necessarily expected other player groups to participate. I figured they would hear about it, but not necessarily experience it from multiple, overlapping perspectives.
But here we are.
It's been an interesting experiment, largely because I often include multiple groups in the same world for verisimilitude, but rarely do so many of them interact with the same event from so many different vantage points. (In my old Mage: The Ascension game, the cabal heard about a massacre from my Sabbat game and investigated it, before determining it wasn't connected. That's roughly as intricate as previous encounters have been — ships passing in the night, or the occasional meeting between two groups.)
Here's what we've seen so far:
1) The Shields of the Sorrowfell are shopping, contemplating two apocalypses on the horizon, when they receive a panicked sending from a patron, saying only, "Wherever you are, you need to come back. Something is attacking Scandshar. It’s bad." They arrive and feel the horrible dread that comes from being within a few miles of a death avatar, eventually making their way through deserted streets until they find the death-god and her cohorts. When they make contact, the battle lasts maybe half a minute, but it's an intense thirty seconds before the goddess is banished and her cohorts are all slain. They take out the rest of the invading army between sessions, because running thirty combats doesn't sound like anyone's idea of fun. They leave behind one dark elf to be interrogated by city officials.
2) FLAILSNAILS muscle wizard Barnabus Sleet is working on a scam to claim the bounty on the Shields of the Sorrowfell, and the timing is such that he contacts them just as they're moving into the city to fight the dark elf invasion. As such, Sleet actually arrives on site first, and begins fighting dark elves and trying to get building fires under control while also trying to figure out just what happened here.
3) FLAILSNAILS Specialist Ribbon, her girlfriend (Sapphira), and a dark elf ally (Alaic) spent the morning of the Winter Solstice running from assassins. When they used a teleport to spend solstice with Sapphira's family, they missed the battle, although sometime in the late afternoon, everyone in the settlement of En'amanisrahd could feel the creeping dread whenever they looked at the cloud bank forming north-by-northeast. By midnight, they learned what happened; they also learned Alaic was a turncoat elite assassin from the invasion force, who fled ahead of the coming of the death-goddess because she started to doubt her mission. In the aftermath, however, she will reveal all she knows to the intelligencers of En'amanisrahd.
(Spoilers for Castle Whiterock: the FLAILSNAILS crew saved Alaic Sorethin before she bled to death in the secret domain of House Forlorna. In my game, since I knew the drow invasion was coming, I made her one of the drow harlequins sent ahead to help make sure the city was ripe for invasion. Alaic and some allies made a detour to the megadungeon ensure there was no interference from House Forlorna. The superweapon House Forlorna was attempting to torture out of her was actually intelligence regarding the approaching death-goddess; they only knew the dark elves of Cinlu Tlurthei had acquired some manner of trump card that would let them invade the surface, although they did not know the particulars.)
4) The others in the FLAILSNAILS crew were at Castle Chilikov when the invasion hit, and so maybe noticed the storm clouds and the weird sense of foreboding, but otherwise only heard about it after the fact. However, a small trickle of refugees has since populated the castle as it's being rebuilt.
5) Fresh from a delve into the Barrowmaze, a group of lower-level adventurers happened to take an extended stay in Scandshar in the hopes of finding a black market for magic items. This extended investigation took them through Winter Solstice, and so they were at ground zero when it started. (The only reason why they weren't in the Market Square when the drow goddess first emerged is because they noticed something was wrong, and started heading back to their inn rooms to resupply.) After battling their way through dark elf assassins and rampaging ghosts, they finally found a safe place to hide, only to be totally surprised that the invasion was already over when they checked the street the next morning.
I found that the players in scenarios #2 and #5 were initially confused by what was happening, as they had little context for it. (I haven't determined if this is good or bad yet — the characters should certainly feel confused and overwhelmed, but I don't necessarily want the players to feel that way. On the other hand, how do you prepare someone for an outside-context problem?) Scenarios #3 and #4 were much more gentle, as people heard about the aftermath rather than participating. (And those sets of players knew something was up by the time I broke the news in-game.)
Scenario #1 of course had the highest stakes — this was their city and their allies, and if they lose, it might mean the collapse of the whole world, given time. (The FLAILSNAILS people can always leave if the world becomes an uninhabitable thanatopic theocracy, but for everyone else, they live here.)
It's probably also noteworthy to mention that the fight with Kiaransalee had five potential phases, each with varying levels of difficulty and stakes. We only encountered four of these potential outcomes:
1) The Shields of the Sorrowfell stopped the goddess' cultists from acquiring ritual components in the giant tombs beneath Tovelka, the event which kicked off this whole plotline.
2) Someone (probably the Shields of the Sorrowfell) stopped her cultists from performing the ritual in the Vault of Gnashing Teeth.
3) Someone stopped her while she was freshly summoned in the Vault of Gnashing Teeth. The death goddess is still here, but in her weakest form.
4) Someone stopped her when she was freshly summoned on the surface. She has gathered power from annihilating a city in the Underdark and from killing people in the streets, but she is not at her full deific strength yet.
5) The occupation of Scandshar grants enough supplicants and notoriety that her presence in this world now bears the strength of a fully-incarnate deity.
Also, note that the defeat of a drow goddess of death and slavery did make the world a better place; slavery is likely to be outlawed in Scandshar after centuries of somehow remaining legal. Sometimes, just punching the symbolism makes a difference.
