Now and again, the opportunity comes up to develop a sub-game within the campaign proper. My favourite example of this was my Riding a Giant Tadpole Over a Waterfall into a Lake Full of Giant Pikes(tm) system that I developed for an old Ryuutama game. This week, due to reasons too complicated to get into, I have to devise a new one, which I am provisionally calling Guiding Five Hundred Refugees Across a Wilderness While Possibly Being Pursued by Giant Swans and Swanmays.
My normal rules for wilderness travel are more or less what one finds in the Rules Cyclopedia. Each day, roll 1d6 to see if there is an encounter (usually 1-2, depending on the environment), and each night, roll 1d12. But that's for a group of, say, 4-12 people, inclusive of PCs and entourage. When there are five hundred non-combatants involved, the calculation changes: they are going to be moving more slowly than usual; they are going to draw much more attention (especially in open areas); and they are going to occupy a wide area of ground in which an encounter might take place (is the encounter at the van, to the rear, or to one flank or another?).
So, the tasks break down as follows:
1. Calculate distance coverage. Each individual occupies 1m of space. So if 500 people are walking in line, they occupy 500m. This is a little artificial, but represents the fact that when a large group of people are walking in a wilderness area, they will tend to walk in small clumps of ones, twos or threes, often with some distance between the groups. 500 people will occupy on average 500m of ground.
Then plot the walking column as a sequence of 50-person numbered squares. 500 people will occupy 10 such squares, thus:
Ask the players to position their PCs in one of these squares, 1-10. There is no requirement for PCs to all be in the same square.
2. Calculate chance of encounters. For a group of more than 50 people, the chance of an encounter increases. If the chance of an encounter is normally 1 in 6, it becomes 2 in 6; if the chance is normally 2 in 6, it becomes 4 in 6, and if the chance is normally 3 in 6, it becomes automatic.
3. Calculate speed. The column moves at the rate of its slowest member.
4. Roll for encounters each day and night as normal. If an encounter is indicated, roll for encounter distance as normal, but also roll 1dx, where [x] corresponds to the square in the column at which point the encounter takes place. For instance, if the encounter is 20 orcs, and the accompanying roll is an 8, this means 20 orcs appear at square 8 on the column.
5. Check PC reaction speed. If a PC is within the square at which the encounter takes place, roll for surprise as normal. That PC can react to the encounter. A PC can also react if an encounter takes place in a neighbouring square (if travelling in forest, hills, badland, etc.) or up to 5 squares away (if on flat ground in the open) - again, roll for surprise as normal. PCs who are too far away from an encounter to react must be alerted. An alert will spread up and down the column from the square in which the encounter takes place at a rate of 1 square every other round.
6. If a PC is not present to react, roll the reaction dice for both the creature encountered and those travelling in the column. For those travelling in a column, on a 2-3 the refugees flee; on a 4-6 they are panicked (roll again in one round with a -4 penalty); on a 7-9 they freeze in fear (roll again in one round); on a 10-11 they are brave (roll again in one round with a +4 penalty); on a 12 they stand their ground.
Should be useful with modifications for any journey involved large numbers of people. I'll test it out on Friday and, possibly, report back on the results.