Next session, my players have to defend their town against a monster army. Since a lot of creatures will be involved (no armies though), I don't want to bore them with rolling for each NPC separately. I made up the following simple troop combat system:
1) I add together the XP for both sides and look up the closest CR value. So there are no longer NPCs but only two CR values.
2) Both sides get a d4 combat roll. They do damage to the opposed side depending on dice result:
1: no damage
2: 20%
3: 30%
4: 50%
So in average both sides suffer from 25% HP loss each round, being killed after 4 rounds. This is based on Bestiary statistics - a CR x creature can kill another one in this amount of time, in average. Independant of the CR, actually.
3) If a side can't attack, it gets no roll.
4) If the CR of one side is higher, modify as following:
CR x+1 vs. CR x: 1d4+1 vs. 1d4
CR x+2 vs. CR x: 1d4+1 vs. 1d4-1
CR x+3 vs. CR x: 1d4+2 vs. 1d4-1
CR x+4 vs. CR x: 1d4+2 vs. 1d4-2
(probably not usable beyond)
1d4+2, 1d4-2 etc. can result in new values:
-1: no damage
0: no damage
...
5: 60%
6: 80%
5) The amount of dead creatures is the squared health loss. So with 30% health loss 0.3*0.3 = 0.09 = 9% of the creatures died. Multiply with the creature amount and round down. If one side is a single creature, accordingly it will die only to 100% health loss (or more).
6) PCs battle single creatures as usual.
What do you think? And are there alternatives out there?
You could just use the troop subtype. It's what I did when I statted a out an army. It's also handy when a PC hires a crew or something
Hmm, thanks. Troop subtype covers a lot, but for my battle it's partially too abstract (always Gargantuan size etc.) or has awkward rulings (always hitting etc.).
I want quick martial battles, with several creatures. With roughly the same outcome as if they battled via rolling. Guess I will stick with my system...
The always hitting is what troops threatening at all levels. As it should be.
A battle against an entire army should NOT be a quick battle, but that's just me.
Looking at your system, it honestly looks way more complicated. If you have to roll and look up several tables to figure out the result of one group of foes fighting another, that slows things down significantly. At least with the troop subtype, you only have to do damage or a Reflex save for ranged attacks. The weaker troop will naturally die first.
It's not intended for an entire army, it's for a few creatures on both sides. Something like 1 to 12 per side. The wording 'several' was probably misleading.
Calculating CR might be a pain in some cases, but in others it's easy. If you know a single orc is CR 1 and there are 8 of them, CR 7 is computed fast. The actual rolling is just 2d4, that's less GM rolling than in most normal encounters. Damage can be noted like IIII II (for 70%) which is also simpler than normal HP notes.
If you feel offended that I dismissed your proposal so fast and completely, be assured I did read troop subtype's text twice and carefully, in the hope for some inspiration.