#### Nickolaidas

##### Explorer

Basically, I take the rules of "Handling Mobs" in DM Guide page 250, and expand on them a little.

My design is the following:

An army has a total of hit points based on Monster HP x Number of soldiers.

The army has five stages of effectiveness, based on the amount of hit points. The effectiveness is a multiplier which affects damage per round.

100% effective = full hit points

75% effective = total hit points down to 3/4

50% effective = total number of hit points down to 2/4

25% effective = total number of hit points down to 1/4

0% effective = army destroyed

NOTE: A change in effectiveness takes place in THE BEGINNING OF THE NEXT ROUND!!

Each round the army chooses how to attack, based on a regular / unique attack it has.

Damage is multiplied based on how many soldiers hit.

Repeat each round until an army is routed or destroyed.

Note: An 'army' which is composed of a single unit, i.e. the Tarrasque, has no penalties for lesser effectiveness, and always hits once, regardless of enemy AC.

EXAMPLE BATTLE

An army of 50 guards attacks an archfiend to protect their city from demonic invasion. Initiative is rolled, and the guard army goes first. The guards have 16 hit points each, giving them a total of 800 hit points. The Archfiend is a single monster with 400 hit points.

ROUND 1:

The guards need a 20 to hit the archfiend (because it has an AC of 23). Based on the Handling Mobs rules, this means that 1 out of 20 guards hits the monster this round. Since the guards are 100, this means that the multiplier for damage is x5, and the effectiveness is 100%, which means no penalty. The guards roll 1d8 and get a 6. Multiplied by 5, the guards gave the Archfiend a total of 30 hit points of damage. Of course, considering the fact the monster is immune to normal weapons, the damage is in turn, turned to zero.

On its turn, the Archfiend chooses to use a Mass Fireball spell instead of attacking once in melee. Rolling the dice, the spell causes 200 hit points of damage (theoretically - I'm not even sure if the spell can cause so much damage). The guards roll a saving throw (once, affecting all), and fail, taking 200 hit points of damage, bringing their total hp to a 600. This brings their effectiveness down to 75%.

ROUND 2:

The guards keep doing their thing and roll 1d8 for damage against the Archfiend. They roll a 4, which multiplied by 5 makes it a 20. However, their effectiveness is down to 75%, which means they get a multiplier of 0.75, bringing their damage to a total of 15 hp this round. Again, all that damage is negated because the damn thing is immune to mere weapons.

The Archfiend makes another Mass Fireball spell and the guards fail their saving throw, taking another 150 damage, bringing their hp total to 450 (still at 75% effectiveness). Or it could use a single melee / ranged attack, or do something else ...

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EXAMPLE 2 - ARMY VS ARMY

2000 human soldiers vs 1500 orcs

ROUND 1:

2000 guards (each having 18 hp) give us a total of 36.000 hp (THAT'S A LUTTA NUTS!!) AC 16

1500 orcs (each having 22 hp) give us a total of 33.000 hp. AC 13

ROUND 1 - Guards won initiative

The guards need a 10 to hit an orc - based on the Handling Mobs rules, half of them hit. They roll a 1d6+1 and get a 4. Multiplied by 1.000, this means they caused 4.000 hp of damage to the orcs.

The orcs need an 11 to hit the guards, so they get the same treatment and get half of their units to cause damage. They roll a 1d12+3 and get a freaking 15 - multiplied by 750, to a total of 11.250 hp this round.

ROUND 2

The guards are fewer than 27000 (their 3/4 hp total) which means they're now at 75% effectiveness. Their damage will now get a 0.75% multiplier. They roll for damage, get a mere 2, multiplied by a thousand, and then by 0.75 for a total of 1500 hp.

The orcs have a current hp total of 27500, which isn't enough to take them to 3/4 of their hp total, which means they're still fighting at 100% effectiveness. They roll for damage and get a 10, multiplied by a thousand to bring a devastating blow of 10.000 hp to the guards.

ROUND 3

The guards have seen much better days ... with their current hp total at 14.750 - less than half hp total, they're now at 50% effectiveness. They get a multiplier of 0.5 each time they do damage.

The guards roll for damage and get a 6, multiplied by a 1000 and then a 0.5, to total of 3.000 hp.

The orcs (still at 100% until the next round), attack and get an 8. Apparently, Gruumsh favors his sons this day, to a total of 8000 hp of destruction.

ROUND 4

The guards are a shadow of their former fighting strength, with a mere 6750 hp pool, less than 1/4 of their total hp - they're now down to 25% effectiveness, giving them a penalty modifier of 0.25. They make a desperate attack at the orchish horde and roll a 4, causing them a total of 4x1000x0.25 damage, which translates to 1000 hp. In short, they're screwed.

The orcish horde has FINALLY began to weaken, with a hp current total of 24500, which is (by an inch) less than 3/4 of their hp total. They're down to 75% of effectiveness. They roll for damage and get a terrifying 11, multiplied by a 1000 and then by 0.75, to a total of 8250 hp. This surpasses the current max amount the human guards had - the human army is completely butchered, down to the last man.

Remaining orcs: The orcs began at 33000 hp and finished at 23500, which means that out of 1500 orcs, only 1068 remained (divine the remaining hp total with the hp an individual orc had). The horde feasts on meat and wine as they celebrate their victory during the night and honor their fallen comrades.

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So, what do you guys think? Does this system work?