Yeah, it works, but I'll be modifying it. No breakthroughs/setbacks, though, as it's all survival against a barrage of enemies.
At the moment I'm using:
Each turn, d20x3 people will die. Possibly more, possibly less.
They can work out what to do, but here are some suggestions:
• Survival – Resolve, Tactics, Sneak, Spellcasting could all allow more people to live through their round. DC20 will remove a multiplier from the d20 roll. A critical hit will stop anyone from dying. A botch will make the result x4.
• Exhaustion – Intimidate and Resolve will help spur people on. If there is not a check against exhaustion each turn/every six hours, then the group will ALL suffer a -1 to their rolls unless there’s some anti-sleep ability. They will have 1 level of fatigued at the start of the next scene if the penalty remains at the end of this challenge.
• Healing – A Medicine DC15 will add 1 to the population count, +1 per 4 above the DC. A crit will double the amount, to a maximum of that turn’s casualty roll.
• Hiding – Blend, Disguise, Sneak or Survival allows the group to camouflage the caravans, with a DC10 to subtract 1d3+Dex from the casualty roll.
• Choosing the Right Paths – Search, Investigate, Survival to search for a good place to go. Will add +2 to one person’s roll next turn. On a critical result, will skip one six-hour increment.
• Repairs – Craft or Knowledge roll DC15. Equipment gets damaged. After suffering enough casualties, a repair roll will be mandatory for a PC or NPC. A failure means -1 to all gear checks until the gear is repaired. A critical means +1 to gear checks for the next check.
I'm really good at winging it so any unorthodox ideas which can't be covered by these, I'll find something for.
Also NPC contacts have been a big thing, especially given that in their group of survivors, losing a blacksmith means NO weapons repaired back to a good quality. Losing a priest means less healing. This means that while everyone's doing their thing, the PC's can call on them for a bonus, at the risk of putting them in my evil GM spotlight and therefore risking their survival.
Hopefully that'll work as something quick if I can't read through the narrative combat by then.