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View Full Version : D&D 5e/Next [PEACH] Off-Screen NPC vs NPC Combat System



Wryte
2018-02-27, 06:52 PM
In tomorrow night's session, my players will be aiding the city guard in a raid on a thieves' guild stronghouse. The stronghouse has two entrances on opposite ends, one of which will be taken by the party, and the other by a squad of beefed-up Guards and their sergeant. In order not to slow the game down by having to roll out off-screen combat for two factions of NPCs, I've written up a system for determining how the battle goes with a single opposed roll per round.

Each round that there are members of both factions in the same room as one another, on initiative count 1 I'll call on a player to roll a d20 against me, with the results determined by the difference in the rolled values.

* 0-4: Both sides hold their position. One NPC on the losing side takes 1d8 damage.
* 5-9: Both sides hold their position. One NPC on the losing side takes 2d8 damage, or two NPCs take 1d8 damage.
* 10-14: The losing side back by one room, and may be pursued by the winning side. One NPC on the losing side takes 1d8 damage.
* 15-19: The losing side back by one room, and may be pursued by the winning side. One NPC on the losing side takes 2d8 damage, or two NPCs take 1d8 damage.

Any side that rolls a natural 20 deals 1d8 damage to a member of the other side. Any side that rolls a natural 1 takes 1d8 damage to one member of their side. Whenever a side takes damage, any member that has a limited resource (spell slots, potions, etc.) may expend one to cancel out one of the damage rolls.

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Ideally, this system should result in the guard NPCs having an impact on the combat by chipping hit points and resources off the thieves before the party encounters them, without the guards outshining the party and clearing half the dungeon without them, and without slowing the game down for the party or making me do too much bookkeeping. My main concern is whether 1d8/2d8 damage is going to be too much when the HP values of the NPCs on both sides run between 30-60ish. Secondly, I'm wondering if I should include any kind of modifiers in this system. For example, should I be giving both rolls a bonus to their result equal to the number of NPCs on each side in the fight? Should I change the damage to be based on the number of NPCs on the winning side (ex., instead of 1d8, take xd4 where x = 1/2 the number of NPCs on the winning side, rounded down)? Should sides gain advantage on the d20 roll depending on the terrain, or would that just be complicating things for myself?

Crisis21
2018-02-27, 07:18 PM
This looks okay at first glance. 1d8 doesn't sound like too much, really given the totals you provided. After all, combat should carry the risk of severe wounds or death before the PCs show up.

I'd suggest one tweak: If a particular side has clear numerical superiority (ex: twice the number as the other side for example) then their d20 roll is made with advantage. If it's an excessive numerical superiority (ex: one side has 4x the number of the other side) then the outnumbered group also makes the roll with disadvantage.

Argothair
2018-02-28, 03:23 AM
Kudos to you for involving NPCs in combat in a meaningful way, and for being willing to streamline the parts of NPC v. NPC combat that aren't interesting!

I like your general idea of comparing rolls and seeing who gets pushed back and who takes damage. One feature *I'd* want in a rule like this is that units who are fighting should take damage even when they have a slight advantage over their opponents. E.g. suppose I send 3 thugs wearing green bandannas to go fight 2 thugs wearing blue bandannas. All of the thugs have exactly the same physical and mental traits at the start of the fight, and they're fighting on a flat sandy beach that stretches on forever. Most likely, the 3 thugs will eventually win...but they're going to be sandy, tired, and bruised at a minimum by the time the fight is over, and more realistically, most of them will probably have some severe injuries.

Same result if I substitute ninjas, or machine gunners, or stormtroopers, or thieves, or goblins. If you fight somebody at or near your level, and you don't have some kind of overwhelming tactical advantage, they're going to hurt you back, even if you 'win' the fight.

Another thing to note is that the difference between 2d20 will usually be quite small. Like, of the 400 conceivable ways to roll 2d20, 30 of them will get you a difference of exactly 5, but only 2 of them will get you a difference of exactly 19. A difference of 5 is 15 times more likely than a difference of 19. So I would use a chart like this:

Each team rolls 1d20 and then adds +2 for each person fighting on that team. For example, if a 3-person team rolls a 9, their score is 9 + 2 + 2 + 2 = 15. Subtract one team's score from the other and call the difference "X".

If X is...
* 0-5: Both sides hold their position. One NPC on the winning side takes 6 - X damage. One NPC on the losing side takes 6 damage.
* 6-9: The losing side is forced to make an orderly retreat by one room. Two NPCs on the losing side each take X damage.
* 10 or more: The losing side panics and breaks, fleeing into the next room with their backs to their opponents. All NPCs on the losing side take X damage. The losing side has disadvantage on its next combat roll.