Are there any issues with creating creatures that can make multi-target melee attacks?

Question

The Issue

Looking through plus-sized creatures in the 5e Monster Manual, I am unable to find any monsters that can target more than one creature with a single melee attack. I would think that a huge-size giant, for example, could swing an axe in a large enough arc to hit several playable characters at once. Stat block descriptions for melee attacks always specify “one target”, indicating the possibility of multi-target attacks, but from what I can tell this is an unused feature. Attack descriptions for larger-sized creatures do generally have a longer reach, befitting the creature’s size, but that’s the extent of it.

Why It Matters to Me

I would like to homebrew a few creatures that can target more than one creature in a single melee attack, but I am suspicious about the fact that RAW materials do not seem to include such mechanics. I suspect multi-target melee attacks are absent for a good reason, and I would like to learn why this might be problematic before I unleash such a creature against my players.

Question

Is there a specific game design reason why I should not create a creature with a multi-target melee attack? Specifically, I would like to edit creature stat blocks that would read like this:

Morningstar. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 21 (3d8 + 8) piercing damage.

to read like this:

Morningstar. Melee Weapon Attack: +12 to hit, reach 10 ft., two targets. Hit: 21 (3d8 + 8) piercing damage.

Is this a problem? Could making this change result in a game-breaking problem, or absurd outcome?

Answer 1

In 5E, the design standard seems be that almost all attacks - especially weapon attacks - feature a separate roll for each target. An “attack roll” in 5E is by convention a single attack vs a single target. Multiple target attacks generally have separate attack rolls made by the attacker (as in the case of multiattack actions), but if not, there's usually no attack roll and instead each target makes a saving throw to avoid some or all of the effect of the attack.

For melee attacks, there are two exceptions: the variant "Cleaving through Creatures" rules in the DMG and the Battle Master's Sweeping Attack manoeuvre, both of which allow an attacker to target a second creature as if making a second attack, but use the result of the initial attack roll. Both have limitations on when they can be used, though, and aside from reusing the initial roll, both are a second, separate attack. (Thanks to KorvinStarmast and Slagmoth for pointing these out.)

There are more examples of single attack vs multiple targets when it comes to spells: auto-hit spells like Magic Missile, which forgo a roll altogether (and as a result cannot critically hit), and unusual spells like Sleep or Color Spray which have the caster roll for a number of hit points of creatures who will be affected (but these spells don’t inflict damage).

An attack that hits more than one target with a single roll has several strengths and drawbacks that are not already present in the system:

• a single roll will be compared against multiple, potentially different armour classes - not gamebreaking, but it may remove some tactical options;
• it allows a creature to potentially score multiple critical hits with a single die roll - something not intended by the system;
• most importantly, there may be circumstances in which advantage or disadvantage applies against one or more targets, but not all - in which case, do you apply it to the roll or not? Rules for advantage and disadvantage may not allow for this case, and may become more or less powerful than intended depending on how you rule this.

I think these are all reasons why this was not a feature included in the game design, and so I’d be cautious about adding in your homebrew creations.

Answer 2

There's a few things you need to think about.

One of those is: what happens with Opportunity Attacks? Can the creature wallop you and your buddy because you tried to leave its reach, or can it not use this ability?

A second one is: what happens with creatures who are not close together? The attack, as written, could hit the person on my left and the person on my right, but leave me unhurt. That's a little odd. Similarly, you could attack someone in front of you and someone behind you. Or you could attack two people who have something massive between them, like a huge rock.

You also need to consider how this attack works with mechanics like (Dis)Advantage (especially if the target is the source, such as when one target is Dodging and the other is not) or effects that cause bad things when you make an attack (like taking damage whenever you attack, or one of your targets being under the effects of Sanctuary, your opponent having a Reaction to being attacked that stops the rest of your attack, such as by knocking you out)

Ultimately, it might be easier to model this by turning it into a spell-like ability that targets an area and forces a saving throw on the defenders. That way, at least mechanics-wise, you won't run into any weird situations and the end-result should be pretty much the same.

Answer 3

It may depend on an actual creature stat block

But there already is precedent for this potential type of multiattack in the Ranger's 11th level Multiattack Whirlwind Attack option (if you are having separate rolls):

You can use your action to make a melee attack against any number of creatures within 5 feet of you, with a separate attack roll for each target.

The Battlemaster's Sweeping Attack is another, but utilizes a limited resource:

When you hit a creature with a melee weapon attack, you can expend one superiority die to attempt to damage another creature with the same attack. Choose another creature within 5 feet of the original target and within your reach. If the original attack roll would hit the second creature, it takes damage equal to the number you roll on your superiority die. The damage is of the same type dealt by the original attack.

Creature size and reach

Extended reach beyond 5' is not something that all (or necessarily most) Large creatures or bigger have. The assumption that the majority of large+ creatures have long reach is not an accurate one.

Completing a stat block

As I said earlier, without knowing the rest of a homebrew creature's stat block and planned CDR, it's very hard to say if this is a reasonable ability. There are too many interactions to consider (number of attacks, other abilities, etc.) that can influence a judgement.

Action Economy

A large portion of 5e is about action economy. Short-circuiting this by creating additional attacks outside of the standard (via a homebrew multiattack, legendary actions, etc.) can affect creature CR and our ability to respond to whether or not this will work for a particular homebrew creature.

Answer 4

You need to use two heterochromatic d20s. Aside from that, this is fine

I did this for a couple of homebrewed monsters and a homebrew monk tradition. It worked fine, except that adjudicating advantage and disadvantage was kinda complicated. To solve that, we use 2d20 for such attacks, with a blue d20 being the normal number and a red d20 being the one that is used if advantage or disadvantage applies to a creature. This works a lot better than allowing the attack to conflate advantage and disadvantage from multiple targets just because there is only one attack roll, and-- while the math is kinda weird because the two dice are shared between targets-- the distribution seems to work out okay.

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Some extra advice, from my experience:

• You are going to want to specify 'up to two targets in range and who are within 5 feet of one another' rather than just saying 'two targets'. Being able to hit an enemy at your front and an enemy at your rear isn't something I wanted my sweeping attacks to be doing, and I doubt it's something you want either.
• Like characters with the War Caster feat, these creatures work best when they are using off-turn Opportunity Attacks to negatively affect other creatures in addition to the one provoking the reaction.
• Once the players learn these opponents can do this, expect them to never again use a formation vulnerable to such attacks around such creatures, unless you have very significant other factors encouraging close formations in the party.

Answer 5

The Problem

The thing to remember with adding targets to an melee attack is that you add significantly to the damage output of the creature.

If a monster can hit 1 target a turn with a 50% chance to hit and do an average of 9 damage per hit, and you add a target (assuming separate attack rolls), your average damage output goes 4.5 hp per round to 9 hp per round. Adding a third target makes it 13.5, and so on.

This is why spells that hit multiple targets usually have less damage per target than spells that hit a single target.

Possible Solutions

• Option 1: When adding targets reduce the damage that a single hit does. This will mean that the damage put out by the attack will be more consistent per turn.
• Option 2: When adding targets reduce the chance to hit. You will hit less but a hit is more significant.
• Option 3: Make It a special attack that can only be used sparingly (recharge or daily)

Answer 6

Harder to determine appropriate Challenge Rating

There is a table in Dungeon Master's Guide, pg. 273 where you can determine a monster's offensive CR.

For example:

A monster with multiattack 2 that deals d6+2 damage per hit, has 6-16 damage per round. This monster offensive CR is between 1/2 - 1.

A monster with multitarget 2 that deals d6+2 damage per hit, has 3-16 damage per round. This monster offensive CR is between 1/4 - 1.

With higher number of multiattack/multitarget, the variance grows even higher.

A monster with multiattack 3 that deals d8+4 damage per hit, has 15-36 damage per round. This monster offensive CR is between 2 - 5.

A monster with multiattack 3 that deals d8+4 damage per hit, has 5-36 damage per round. This monster offensive CR is between 1/2 - 5.

Those example is just a rough estimate, but it gives you the idea that you will have harder time to estimate how well your creature performs in combat. Against one party, it might perform well because there are two or three targets available most of the times, but against another it might be crushed easily because it only gets to hit one target all the time.

How well this creature will perform with multitarget attack depends on:

1. Engaging as many enemies as possible, making it more dangerous.

2. Positioning itself, possibly provoking opportunity attacks and is highly dependent on limited mobility.

3. Availability of targets. Most of the time, you will only engage one or two enemies at once, so you will always deal less damage than normal multiattack. (n-targets vs n-multiattack)

In short, your encounters might be swingy. Be careful if you want to use this mechanic.

Answer 7

The thunderclap cantrip (EEPC, p. 22; XGtE, p. 168) hits each creature in a 5-foot radius.

There is precedence for this. Don't be afraid to use it.