As the DM I couldn't be happier.
They basically sold samples of 4 different strains of a gnarly zombie virus, the lab used to make them, and all the notes the crazed wizard used to make them. And 1 of the party members almost died because of one of the diseases on the way back to town because he was out of spell slots, the disease kept lowering his CON stat, and part of the sickness was preventing him from getting the benefits of a long rest.
Sounds like you're getting lots of opportunites to make them regret it lol.
In terms of bad decisions the party has made this is definitely up there AND ties into some of their other bad decisions quite nicely.
It's also going to solve a problem they've been ignoring by making it a different problem in terms of a near by area where a port city was conquered by a different crime lord who has declared themselves a new feudal lord and that that area is his.
The crime lord that they sold the zombie plagues to would rather see that port city in ruin than the hands of another, and he now has the tools to do so with as simple as a contaminated food shipment passing through the area.
Why does this sound more like intended consequences than unintended consequences
The best part is that that's just the tip of the iceberg really, the place where they got the samples of the zombie plague was bombed out with a 5th strain of said zombie plague that was from a bomb dropped by a kingdom of goblins that they helped 2 years ago. And by helped I mean they helped them found their kingdom.
They never asked the goblins what kind of kingdom they were going to make if they were given the Spell Forge rather than destroy it like the other factions wanted. The kingdom they were going to found turned out to be not a good place (shocker) and the goblins were able to restore the Spell Forge (and improve it) in their absence by cutting some deals with an evil god.
Basically The Great War is starting and the first domino was knocked over 2 years earlier and they didn't even notice while they were adventuring across the country side. And they knocked over a few more as well.
This will also play into us busting into One Page Rules for some wargaming to see how things shake up.
I don't know which faction is going to win but I know the world will never be the same after.
Ah the wonderful wonderful world of consequences
Omg I love it 😂