Don’t split the party!
This is sage advice among roleplayers, passed down from generation to generation like stories about the Boogeyman – a warning to the young and foolhardy espoused by wizened Players and Game Masters alike: “Don’t split the party, or else!”
Or else what?
Or else this adventure – which was carefully designed for a full group of six people who haven’t split up – will destroy you.
That’s the main answer to this question. You can’t split the party because the encounters in whatever adventure you’re playing were designed to challenge a specific number of characters and splitting the party changes the number of characters in those encounters, making them too difficult to overcome. There are a couple of other practical, but equally meta-game oriented reasons as well. Splitting the party creates more work for the game master, who has to divide his time and attention between two groups of people doing two different things. Also, splitting the party inevitably creates downtime for some folks at the table while they are waiting for the action to roll back to them. All of these are pretty good reasons. The problem is, they are all reasons the game master and players have for not splitting the party and none of them are reasons the characters have for not splitting the party.
That’s not to say that characters have no in-game reasons to stick together. I mean, the general rule of safety in numbers is a pretty good rule, especially while exploring unknown dungeons, and most of the time the in-game reality of safety in numbers is a good enough justification for sticking to all of those meta-game reasons that are really keeping the party together.
But sometimes, there are really compelling in-game reasons for the party to split up. Maybe the party is chasing someone and splitting up will help cover his or her escape routes more effectively. Maybe the party is searching for a something and are pressed for time. Maybe stealthy party members see an opportunity to flank their enemies or otherwise gain an advantage. Maybe Wroth-Wrath the barbarian thinks the party should go East while Gobo the dwarf thinks they should go West, with each one eventually leading a few people in either direction. In these situations, and in pretty much any other situation where splitting up is an option, the meta-game reasons for sticking together carry much more weight in the eventual decision than anything the characters may be thinking, and so almost always everyone sticks together regardless of what they think the characters would actually do.
Moreover, Game Masters often reinforce the don’t split up approach by “throwing the book” at people foolish enough to try splitting up, perhaps saying something like: “Alright, you guys asked for it – this fight was suppose to be for all six of you but now Wroth-Wrath and the elf are in for it!” And maybe sometimes this is ok – if you know for a fact that an entire orc army is camped down the Eastern passage maybe you shouldn’t go that way.
But more often than not the challenge that lies ahead is mutable – in the sense that neither the players nor their characters know what is around the next corner and so the game master is ultimately free to do whatever he wants. Whatever is “suppose” to be there doesn’t have to be there just because the adventure tells you it’s there. If the players are roleplaying their characters, and there is a logical (or at least compelling and interesting) reason for them to split up then let them do it! Don’t punish them for thinking outside of the box. Maybe scale back the number of skeletons around that next corner or have that owlbear be out to lunch.
That doesn’t mean to make everything a cakewalk either – it probably shouldn’t be feasible for the party to survive a trek across the Bog of Death by heading off in six different directions, and you shouldn’t allow them to succeed at this just because they say that’s what their characters want to do. And there will be many times when it doesn’t make sense to scale back the challenge, but the party will decide to split up anyway. In these situations, try to give the characters an out that doesn’t involve them rolling up new characters. Maybe there is a secret side passage that the characters can reach before the orc army descends upon them (but not before said army is aware of the presence of intruders). Use common sense, but try to give the players plenty of leeway to play their characters in the manner that they feel makes the most in-game sense. Avoid being punitive for the sake of “teaching a lesson” about splitting up the party.
And while the party is split, be as judicious as you can with the amount of time you spend with each group. It may happen that one group runs into much more interesting things than the other, making it difficult to balance the time. In these situations, make good use of cliffhangers as you switch back and forth, and try to get the other group back with the “exciting” group or on to their own excitement as soon as possible. Nobody will care too much if you play a little fast and loose with continuity and the passage of time as long as everyone has something to do. If one group does run into a combat situation and one doesn’t, have the idle players roll some dice for some monsters while they wait their turn.
Remember: most of the time parties will stick together because most of the time that will make the most sense. But when a situation arises where splitting up seems feasible (to the players at least) then you should roll with it.