I would love to hear, once you're done, how this played out among the players.
Finally got some time to piece together a response to this. I think the first thing I should say is that the finale of Zeitgeist lived up to the rest of the campaign, at least for us. The roleplaying gods smiled on us, and the 'big event' approach paid off, lending the final session the weight it deserved. With just a few modications, I was able to make the final encounter sufficiently challenging for my large group (adding a few powerful additonal foes instead of hordes of weaker ones, which the players later said they had been expecting).
Luck also played a substantial role in the encounter itself. Without my direction, little set pieces found their place, and the dice made all sorts of dramatic stuff play out. Then there was the pre-planned twist involving Rumdoom. Neither I nor his player were certain how that would go, or when exactly. But both of us were thrilled when Korrigan started ignoring Rumdoom's demands for an icon. Mostly, this was perforce: he couldn't get the icons to Rumdoom. But the repeated demands and repeated failures added a lovely build-up of tension between the two characters.
It can't have escaped readers' notice that this twist dominated the end of the fight, and Nicodemus' demise was all-but sidelined. This was accentuated by the odd twist of fate which saw Nicodemus speeded up by his addition of a new time plane at the very moment he and Miller came into conflict. Their exchange became quite ridiculous. Then, of course, he was slain with a single bullet, which had an unexpectedly negative impact on Quratulain's player, who took quite a while to get over it.
I have to say I loved the way this played out. Being written out of the story in this way was a fabulously tragicomic way for the prideful mastermind to go. And the shock of his sudden demise will certainly live on in the player's mind longer than any run-of-the-mill epic showdown. (And, I mean, come on: we'd been playing for about ten hours by this point, so a hit-point grind would have been horrible.)
In any case, no one was given a moment to think about it, because events had already taken a terrible turn for the worse. Rumdoom hobbled Borne and then set about destroying the Axis Seal. Again, the timing was perfect. There was no prearranged signal, he chose his moment, and took out the Fire pillar even
before Miller exposed Nicodemus, so the two huge moments overlapped.
When he took out the second pillar, everyone needed a break. Korrigan's player was looking ashen-faced and I've no doubt feared that the campaign would end in ruin. But I had told Rumdoom's player that, while I liked his idea of turning on the team at the last minute (something we'd been building up to throughout the Gyre odyssey), it mustn't allow the whole finale to become 'the Rumdoom show'. I'd got the World Spirit waiting in the wings to set things right.
What I couldn't know was whether the team could fix the ritual the way they wanted it before Rumdoom struck the seal. I was almost certain they wouldn't. What may not have come across in the write-up was how close and tense that all was. Without Matunaaga's speed and Leon's network of portals, there would have been no chance at all. Matunaaga's inclusion was a tip of the hat to his absent player, who had hoped to make it if he could. (And his initial appearance - another nod to Nic's possession of Andrei - drew groans from the others, who couldn't know how easily he would shrug Nicodemus off, and were all too well aware of what a dangerous foe Matunaaga could be!)
Then there was Leon's little 'wobble'. His surprise decision to help Rumdoom took everyone by surprise, including me. Rumdoom's player was thrilled. He began openly taunting Korrigan, and enjoining other players to follow suit. (Uru, who loves throwing a spanner in the works, was severely temped.) The others were appalled. As was I. I realised that a few off-the-cuff remarks I'd made earlier had given Leon's player the wrong impression about how destroying the seal would turn out, and used Kasvarina to set him straight. But his choice was fabulously in-character, focused on misgivings that were brought into sharp focus when Nicodemus taunted them for imitating his grand plan.
It was also the culmination of a seven-year character arc in which the consummate traitor sought to demonstrate that he was in many ways the most trustworthy unit member of all, only to throw it all away in the final furlong. I'd spent so long tempting him to betray the others, to no avail, only for him to suddenly do so of his own accord! Magnificent!
All of this added up to an incredibly intense final hour. We could easily have lost focus by then, gotten punch-drunk, but the way fate and great roleplaying weaved these disperate threads was a joy to behold.
Our session didn't end when Rumdoom struck the seal. I finished the account there because it felt right, and will add the coda (or the immediate aftermath) to the start of my next session report, which I'll post in a few days. Something for everyone to read in self-isolation!