Mobs

This section can help you speed up play when resolving outcomes with large groups of monsters, also known as mobs.

Tips

Follow these tips to smooth a combat encounter with a large number of monsters:

Damage. Use the average damage specified in a monster’s stat block.

Hit Points. If a spell or attack reduces a monster to a handful of Hit Points, assume the monster is killed or otherwise taken out of the fight.

Monster Mobs. Divide a large number of identical monsters into smaller mobs and spread their turns out between the characters’ turns. Mobs of five to eight identical creatures work well, but don’t have more mobs than there are characters.

Average Results

Whenever you would otherwise make a number of D20 Tests for identical monsters, the Mob Results table can help you determine the number of successful D20 Tests the monsters get without having to roll dice. Follow these steps:

Step 1. Determine the minimum d20 roll the monsters need to succeed on the D20 Test using the following formula:

Roll needed = target number − monster’s bonus

Step 2. Find the roll needed on the Mob Results table. If all the monsters have Advantage on the roll (for example, if they’re attacking and have the Pack Tactics trait, or if they’re making a saving throw against a spell and have the Magic Resistance trait), find the roll needed in the With Advantage column. If all the monsters have Disadvantage (for example, if they’re attacking a creature protected by the Blur spell), use the With Disadvantage column. Otherwise, use the Normal column.

Step 3. Read across the table to find a fractional number of successes you can easily apply to the group of monsters. That’s the fraction of monsters that succeed on the D20 Test.

Adjudicating Areas of Effect

When the characters are fighting a large number of monsters, it’s not always practical to use miniatures on a battle grid or some other visual aid. So how do you determine how many monsters are affected by the Wizard’s Fireball spell or some other area of effect?

The Targets in Area of Effect table offers a guideline. To use the table, find the column for the shape of the area, then read down until you find its size. Then check the rightmost column to see about how many creatures are caught in the area. If you imagine that the targets are spread out, decrease the number by 1d3. If they’re bunched up, you can increase the number by 1d3. Of course, an area can’t encompass more creatures than are present in an encounter.

Your judgment always outweighs these guidelines, and it’s fine to err on the side of affecting more creatures. For example, if eight zombies are crowded around a Fighter when the Bard centers a Shatter spell on the Fighter’s space, the spell’s area should definitely engulf all eight zombies, even though according to the table, a 10-foot-radius Sphere includes only three creatures.

Examples

The following scenario shows examples of how you as the DM can apply the guidelines described in the rest of this section.

Eight Zombies surround and attack a Fighter. The zombies’ attack bonus is +3, and the Fighter’s AC is 18, so the roll needed is 15 (18 − 3). Finding 15 in the Normal column and reading across to the Out of 8 column, the DM gets a result of 2/8—two of the zombies hit. Using the zombies’ average damage (4 Bludgeoning damage), the Fighter takes 8 Bludgeoning damage.

After seeing the Fighter mauled by zombies, the Bard casts Shatter, centering the spell on the Fighter. (The Bard trusts that the Fighter will succeed on the Constitution saving throw and survive the resulting damage.) The spell affects a 10-foot-radius Sphere, and the Targets in Area of Effect table suggests that such an area should encompass three zombies. However, the DM decides that all eight zombies (and the Fighter) are affected. The zombies’ Constitution saving throw bonus is +3, and the Bard’s spell saving throw DC is 16, so the roll needed is 13 (16 − 3). Finding 13 in the Normal column and reading across to the Out of 8 column, the DM gets a result of 3/8, so three of the zombies succeed on their saving throws.

Seeing a larger crowd of zombies in the distance, the Wizard casts Fireball. The spell covers a 20-foot-radius Sphere. The Targets in Area of Effect table suggests that area covers ten zombies, but the DM rules that they’re densely packed together and adds 1d3, rolling a 2. So the spell engulfs twelve zombies in its area. The zombies’ Dexterity saving throw modifier is −2, and the Wizard’s spell save DC is 16, so the roll needed is 18 (16 − [−2]). Finding 18 in the Normal column and reading across to the Out of 6 column, the DM gets a result of 1/6. Twelve times 1/6 is 2, so two of the twelve zombies succeed on the save.

Mob Results

Targets in Area of Effect

*Use this column for Cylinders, Emanations (using the size of the Emanation rather than its radius), and Spheres.