Monster Type: Army

 Have you ever read through some old adventure module and come across a room that has 40 orcs in it?  You don't see that much anymore.  Let's talk about that.

Skeleton Army by Adrian Smith

The Appeal of an Army

I don't think I need to defend the idea that it is cool as fuck to fight a horde of enemies.  Orcs, hellhounds, traitor knights, vampire wolves. . . they're all cool.

They're also intimidating in a way that a dragon is not.  Normally, in the boss fight encounters against a singular foe, the players have two advantages:

• They get more actions than the dragon.
• The dragon might unluckily fail an important save.

When the PCs are badly outnumbered, these advantages turn into disadvantages, the danger of which isn't lost on the PCs.

(Things like legendary actions and legendary saves were created to smooth over the advantages in order to create more homogenous combat experience, but it's still a hack.)

The Disbanding of the Army

Why don't we see armies like this anymore?  The big reason is combat complexity.  As editions of DnD got more complex, combat turns started taking longer and longer.  How much did blur slow down combat in 3e?

There's also the push for more complexity in monster abilities.  Each monster has been loaded down with more and more bells and whistles.  This creates more of a burden on the DM, to use and track these abilities effectively.  I'm not saying the trade-off isn't worth it--sometimes it is.  But we should be aware of what we're giving up when we start giving bonus actions to lowly orcs and goblins.

(I've made the argument before that there is a lot of worthwhile differentiation that can come from behavior, rather than the stat block, but that's a different conversation.)

OSR combat moves fast.  A fight against thirty orcs shouldn't be out of the question

Rules for Facing Armies

How many people can you catch in a single fireball?  Maybe 3 if they're wisely spread out.  A dozen if they're densely clustered.  On any other round, tell the wizard that their best fireball opportunity is 2d4+1 (rerolling it every round--let the wizard decide when the best opportunity is).  Armies that are trying to spread out (and have the space to do so) will limit themselves to 1d4+3 within the range of a single fireball.

Can you split up an army?  Easily, if your foes are unintelligent.  Intelligent enemies will avoid splitting up into overly small groups.  If they search for you, it will be with scouting groups that will retreat and seek help, rather than allow themselves to get drawn into a pitched battle.

The most important rules will probably be facing rules: how many orcs can attack your fighters simultaneously?

In a hallway 10' wide (or other chokepoint, I'd say that 3 people fighting abreast is the maximum, while 2 people fighting abreast would be the minimum to hold the line.

While totally surrounded, a cluster of at least 5 PCs has 2 enemies facing each of them.  Smaller groups will have 3 enemies facing them simultaneously.

Armies will, of course, fight as intelligently as they can.  This includes, but is not limited to:

• Having one group fight the PCs head-on, while another group circles around to flank them.
• Sending a runner for reinforcements.
• Trying to lure the PCs into a place where they can be surrounded.
• Using ranged attacks to get more attacks in per turn.
• Using ranged attacks to lure PCs into position.
• Use long-shot attacks (the equivalent of save-or-dies).

Some examples of long-shot attacks and interesting tactics:

• GRAPPLE.  Nets, whatever.  Just pile it on.
• Smoke bombs.
• Setting the place on fire.
• Releasing snakes.
• Start chanting.    After 3 turns of chanting, a person goes blind and feeble every turn.  Lasts as long as the chanting does.
• Start chanting.  It's a very slow polymorph spell, which turns someone into a snail over the course of 3 turns.
• Start breaking all the valuable items in the dungeon while shouting blasphemies.
• Lassoing a PC and pulling them away from the party.
• Refusing to allow the PCs to lure them into a disadvantage.  Instead, they fortify a large room (or critical dungeon junction) and continually insult the PCs for not attacking them.  Although, at this point, you risk treating them like a faction.

*Differences Between Armies and Factions

Armies you fight all at once.  Factions you deal with their interests and kill them off in small groups.

I'll admit, it's a blurry line.  40 barbarians could easily be a roleplaying challenge more than a combat encounter.  Seducing them, bartering with them, getting them to fight your enemies for you, getting them to fight among themselves.

Dynamics

An interesting fight evolves--it's not just 3 orcs marching through the same chokepoint every turn until the whole army is dead.

Unless the army is mindless (and I don't even run skeletons as mindless foes), they'll know when they're fighting a losing battle, retreat, and try a new tactic.

Here are some other ways that armies will mix things up:

Orcs -- Settle it with a contest of champions.  The orcish champion is level 2+1d4, and will fight dirty (suggestion: as soon as the PCs nominate their champion, the orc will launch into combat without any preamble, throwing an axe and then charging).  Losing side clears out of the dungeon.

Bandits -- Will just offer you money to leave.  1d6 x 100s.

Goblins -- Start making a shit-ton of noise, summoning 1d4-1 (min 0) random encounters.

Skeletons -- 9 Skeletons start dancing.  After 3 rounds, they summon a demon of X HD, where X is the number of skeletons that are still dancing.  (Remember that undead are created by inviting incorporeal demons into a corpse.)  Other skeleton spells: mass extinguish, shatterhand (metal shatters upon coming in contact with the skeleton), fear.

Berserkers -- If they don't decide to retreat and try a new tactic, they'll fight to the death.  They bite off the tip of their own tongue.  Each round after that, they'll get +1 to hit, -1 to AC, and +1 to the damage that they both deal and receive.  This is cumulative up to +4.  If it would increase beyond +4, the berserkers instead start killing each other until they are all dead.