How do I adjust the Peril in Pinebrook adventure to be for 5 players?

Question

I am DMing the one-shot Peril in Pinebrook. The game is designed for 4 players, but in the oneshot, it says at one point:

If you have more than four players, they can change the names and descriptions on a duplicate character sheet so that they’ll have unique characters with similar abilities and equipment.

I have never DMed before. I want to adjust the one-shot for 5 players, even though it is meant for 4 players. Do I need to adjust the hit points of the enemies, the DCs of any other events, etc.?

Is there perhaps a formula that is available to automatically adjust hit points and DCs in one-shots to the number of extra players that might be added in the future?

Answer 1

There isn't such calculator, especially since adventure you linked seems to be using custom, very simplified ruleset similiar to 5e, so any tools dedicated to 5e may not work.

For standard 5e, you can use tools like Kobold+ Fight Club, to see very rough estimate of difficulty for the encounter, based on number and level of players vs number and CR of opponents.

In general, it is hard to make a single formula for such scaling, as the concept of Action Economy means things very often do not scale in an easy way - for example, feature called Pack Tactics that gives a creature advantage when ally is near target makes 2 such creatures much more deadly than fighting just one.

For your case, DCs should not be scaled, as they are not in any way dependant on the amount of players - having more characters does not make any single of them better in what they are doing, after all. Scaling either the amount of enemies by 25% (e.g. from 4 to 5) or their HP similiarly should be fine in this case, as the abilities of enemies seem to be rather simple.

Finally, as always, as a DM you are empowered to make adjustments as you go, based on if you feel your players are having too easy or too hard time.

Answer 2

You don't need to change anything

Playing a D&D Adventure with 5 instead of 4 characters is not a big difference. As a matter of fact many official Adventure Books I am aware of suggest a group of 4-6 players with no addional advice to scale the adventures, examples being Rime of the Frostmaiden or Shadow of the Dragonqueen.

This is your first time DMing and you already have a lot to handle, so my advice is to not worry and don't change anything, just run it as it is. Your players will probably not notice a difference, especially if they are also playing for the first time. Your battles and other encounters will in theory be a little bit easier, but this will in my experience not be noticeable to a newbie group. They will very much remain engaging and thrilling to your players.

After playing for a few sessions you might start to get a bit of a feel like: "Oh that battle was a bit easy and I think my players would like a bit more challenge, next time I might add 1 or 2 more goblins or give them a bit more hit points". But that's something to worry about after your first time dming.