Well to be honest I just didn't understand what is fun about killing a non-threatening animal for no reason? And why the characters would want to that?
I mean if the players were bored then there were things they could do to make something happen that would still be logical in-game.
For example the druid could have used her speak with animals spell to talk to the beasts of the forest and maybe learn some helpful information about the brigands' camp (I had prepared some information for this possibility). Or cast find familiar and use the familiar to scout out the surrounding area.
They could have carefully examined the tracks of the brigands to try to determine how many there are and also what race/species they are from the sizes of the footprints.
The things you suggest don't sound as immediately gratifying as blowing something up with a Firebolt.
What you describe doesn't sound to me like
a player who can't make good roleplaying decisions. It sounds like
a player who isn't really interested in exploring the world that you have created, so as to puzzle out the details about the brigands.
When I am a player and one of my fellow party members wants to do something like that, I just say "Hold on, what are we trying to achieve here? What are the ramifications of our characters doing that? Why would our characters want to do that?" Not in a rude way, just emphasizing that we should be making decisions based on some kind of logic. The characters should have some kind of reason for doing what they are doing. We should be imagining what the characters are thinking and feeling based on their situation, abilities, experience, loyalties and surroundings.
I don't think your outlook on play is the same as that of the Firebolt-ing player.
He said his character was a noble and a wizard. Didn't mention anything specific about his personality apart from he was an adventurer seeking fame and fortune.
This is classic in itself -
my PC has no background or motivation other than doing adventuring hijinks . . .
Or if the players were keen to get into combat as soon as possible they could have just told me "We pick up our pace and charge forward with our weapons drawn to try to reach the brigand camp as quickly as we can".
There doesn't need to be any correlation between
the pace at which the PCs are moving and
the pace at which events are narrated at the table. If the PCs are sneaking, but the players are restless, then you can just cut to the scene of the stealthy PCs arriving at the brigands' camp.
I know lots of people enjoy the combat side of D&D and I had prepared some encounters accordingly. It was made very clear in the introduction that these brigands were ruthless and were not going to go down easily, it was going to be a serious battle. And the players had also encountered an NPC in the town who had warned of other dangerous monsters and ancient ruins deeper in the forest. So there were obviously going to be several opportunities for major confrontations. There was no need to randomly attack animals.
Well, my suggestion would be that - the next time this comes up - when a player tells you they want to Firebolt a bird, you narrate something like "As you're eyeing the bird to take your shot, you heard something crashing through the forest towards you!" And frame the PCs into an encounter with one of those dangerous monsters.
In other words, instead of hoping to control the PCs, use your control over the elements that are yours as GM - like the framing and pacing of events - to steer the game in a direction that is more interesting to you.
I would let it happen but there may be consequences. Eg offending the local elves/Druids.
If there are never any negative consequences for Resting whenever they want, then, of course, the group will rest whenever they want.
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On the other hand, if there are actual consequences for resting whenever they want? They get to the treasure hoard and find it emptied out. They get to the adventurer's hall and find all of the lucrative contracts have been handed out. They rest in enemy territory and get swarmed, etc. Maybe they will be a bit more judicious about resting?
My own view is that this sort of relatively heavy-handed GMing - where the GM uses their control over the background and setting to retroactively impose stakes onto player decisions - can lead to an adversarial relationship at the table, and/or to rather passive players who are scared of making decisions because they don't know what will flow from them.
I think it's better to be up-front about stakes. For instance, if the player declares their PC is about to blast a bird, and you want to make this a druidic matter, have a druid come onto the scene as they are about to take their shot: make it an express part of the stakes
before the player commits to their action.
Something similar can be done with resting, though often the conversation might be a bit more "meta".