Preparing for the Main Event

My players in my Ravnica D&D campaign have been building up to a big attack on a Simic laboratory that is being used by a rogue biomancer who is aligned with the Phyrexians in an attempt to infect the most populous plane in the multiverse.

I've been thinking, thus, a lot about climactic battles and encounter balancing.

There are, by my count, six combat encounters the party is likely to deal with over the course of the attack. They're level 10, so resources are rather plentiful and they're pretty tough.

I don't know to what extent the players are going to feel the need to push forward - I'm treating these labs like a dungeon, so while they do run the risk of being attacked should they take a rest, they will be able to complete at least a short rest once or twice during their push.

While this is certainly the main event of tier 2 for the party, it's actually not going to be the finale - they have to face off against my planeswalker villain. I think she's going to be more intent on escaping than fighting, so I might have her planeswalk out at half health or so, but I do think that she should be a tier-4-level bad guy.

But before we get to that, I want to make sure that the lab fight will be sufficiently exciting and challenging while remaining balanced.

I've been fairly religious with the Xanathar guidelines for encounter building, which has yielded some scary moments but hasn't actually killed anyone yet. While I'm not eager for anyone's character to die (though there is ample opportunity for resurrection - the Orzhov even have a whole payment plan structure your friends can get you indebted to) I do want to give the characters some pause. I think the slog of going through six different fights (potentially fewer, as two of them can be RP'd around) might be enough to make the final fight dicey by default.

In fact, as I write about this, I think the key is to make the actual tier 2 finale (after which they'll all hit level 11) the truly scary fight. A kind of wake-up call after the triumph of the big dungeon.

Essentially, I'm going to balance a fight for level 16 (maybe slightly lower) that they'll be fighting at 10.