"They've got us surrounded, the poor bastards."
Last time, I wrote about avoiding the urge to counter a player's success. If the game takes a sudden, dramatic turn in the players' favor, take a moment to collect your thoughts and think things over. It's easy to make a snap judgment that simply denies the players their victory.
So, you're taking a break, sipping your beverage of choice, and wracking your brain. What now? Take heart in the quote above. You're the GM. Any difficulties you face are only temporary.
To start with, success comes with consequences. This is a great rule to keep in mind for things like social checks and character influence, but it applies to things like dropping a balor with a single, lucky crit.
A lucky check or crit can spell the end of an adventure, but it's just one part of your campaign. As a GM, you're always playing the long game. Resist the urge to try to resolve things at the table in the current session. Great campaigns are what keep gaming groups going. Your goal is to make sure that this turn of events feeds into your campaign.
Hang some long-term consequences on to a great victory and make it all the more memorable and pivotal to your campaign. Take a step back, think about what's happening, and turn the event into the flashpoint for your campaign's next act.
It's actually pretty easy to implement, and best of all you don't need to think on your feet in the current session. Just play through the PC's epic victory, and work the consequences of their success into the next session.
Use a little aikido in your campaign. Don't fight against the character's success. Lean into it, turn your thoughts in its direction, and accelerate it out of the characters' control. Fighting against the flow of the game is the surest way to bring a campaign to a halt.
The PCs kill a balor. An alchemist tracks down the body and uses it to create a virulent poison used in a series of assassinations
The good-aligned PCs charm the socks off the evil warlord. He puts them in charge of sacking and burning a halfling village.
The PCs evade every trap in the Tomb of Bror and claim the Hammer of Damnation. The high priests of Jagra dispatch 33 unholy assassins to reclaim it.
Not only have you preserved the PCs' success, but you made it even more important by tying it into your campaign's larger story. By answering a tactical twist in your campaign with a strategic shift, you keep the characters and their successes (and failures) as a central piece in shaping the campaign.
Next time, what to do and what to avoid when you absolutely must respond to a game changing event in the midst of a session.