Thee Dungeon Master's Guide (2014) is full of little tidbits of wildly varying quality. Amongst these oft forgotten rules is a little section called Handling Mobs. Now we have all been there, when our players have levelled up and we want to run an encounter against a horde of low levels mooks to really show off how much more powerful they are now. Running such an encounter with the standard rules would be slow and tedious, having to resolve rolls for potentially dozens of enemies. And that is where the DMG advice comes from.
To put it simply, the DMG solves this problem by removing rolling entirely. Obviously I as a dungeon master love to roll dice just as much as the players, but these sorts of combats, rare as they are, are a happy exception. What the DMG instead suggests is to use a lookup table which links the minimum die roll needed for an enemy to hit (effectively the targets AC minus the attackers' attack bonus) with the number of attackers required to make a single hit. Confused? Yes I was too at first. The example provided clears it up though:
For example, eight orcs surround a fighter. The orcs’ attack bonus is +5, and the fighter’s AC is 19. The orcs need a 14 or higher to hit the fighter. According to the table, for every three orcs that attack the fighter, one of them hits. There are enough orcs for two groups of three. The remaining two orcs fail to hit the fighter.
Running a combat of level 12 players against dozens of skeletons with these rules was shockingly smooth, with the hardest part being coordinating which mooks to move where. The players similarly had a great time here, we used the DMG optional cleave rule to boost melee attacks and of course, as expected, in this encounter AoE spells are king.
I don't think it is a perfect solution though. It does not provide any advice for handling mob HP, which would get tedious very quickly. I was fortunate in that I was using a VTT so tracking the odd skeleton that somehow survives wasn't too bad. If I were running it with pen and paper then I would probably use a combined HP pool, similar to how MCDM's Draw Steel game does for its minions.
Additionally Advantage/Disadvantage isn't touched on here. I defaulted to +/- 5 on the target number if all the creatures making the attack would have (dis)advantage, but I was tempted to just ignore it as the cases of it applying uniformly are few and far between. I don't love doing that since the advantage system is a core gameplay mechanic, and many player abilities work around getting advantage or giving disadvantage. But I fail to see a simple way to handle it without splitting individuals from the mob to be resolved separately, which is exactly what not to do.
But overall I think this is a great ruling that I don't think many people discuss when handling mass combat. What are everyone else's thoughts on it? Are there homebrew systems you like more? And does 5e2024 do anything different?
The new DMG likewise has a big table for figuring out how many rolls would succeed given a target number and number of rolls.
I have two approaches I prefer these days:
The damage pool. Instead of tracking individual damage, you pool damage in a single tally and remove the last monster hit when it crosses the HP of a monster. Add up all the damage and remove a bunch of monsters with an area attack.
Group up sets of monsters into four groups and then roll once for each group. If sixteen skeletons have to save versus a turn undead. Group them into four groups of four and roll four times.
We have a handful of ideas like this in Forge of Foes and the Lazy DMs Companion and released them under a CC license here:
https://slyflourish.com/lazy_gm_resource_document.html#runninghordes