Something that comes up surprisingly often in my groups, is what to do when a player's only option is to use some kind of area effect against a single target? This includes cases such as dragonborn breath weapons, and various spells, often when enemies are resistant or invulnerable to other damage types.

It always seems strange for example that a vanilla black dragonborn spitting acid in a straight line would still arc it over the head of a single target, rather than directing the jet of acid directly against them specifically. Likewise when very large creatures are still only somehow hit once in a giant fiery explosion.

On this issue I've been considering some possible houserules I might use:

Directed Blast

When damage is dealt in a straight line, cone or projected cube (such as for Thunderwave) against a single target that failed its saving throw, the target must repeat the saving throw. If the second save is also failed, then the target suffers the same initial damage again.

The idea is that if a target is hit by an initial stream of acid/fire/whatever then they may still avoid or be hit by any follow through from the directed effect. Thematically it's supposed to represent the same attack being sustained or focused.

Large Targets

If a Large or bigger creature is at least half covered by an effect that deals damage to all targets in the area, then it must roll an additional saving throw for each size class that it is above Medium, and will suffer the initial damage for each save that it fails. Any secondary effects are applied only once at most, regardless of the total number of failed saves.

This rule does not combine with Directed Blast (choose which one to use if both could apply).

This one is intended to reward striking bigger creatures with more of the area of the blast (at greater risk to teammates), rather than just covering the bare minimum required.

I'm curious what people think of any possible balance issues with these rules, or if anyone else has used other rules or has any other thoughts or suggestions? I'm thinking the Large Targets rule will require some kind of adjustment to encounter difficulty either based on the size of creatures, or the number of players with blast effects?

Like I say, questions around blasts come up a surprising amount in my groups; I think because we tend to have heavily themed characters, so while there might be a pretty good mix of damage types across the party, specific characters can face difficulties when an enemy is resistant to their most versatile damage type, leaving them with only attacks or only blasts for their remaining damage type(s). For attacks this rarely seems to be a big deal, but for blasts against single targets it means reduced damage which is rarely fun, as blast spells usually require at least two targets (usually three or more) to be good value.

It also just feels weird thematically to use Burning Hands against one enemy and waste 80-90% of the flames pouring out of your hands, so it'd be nice to have some good houserules in the bank for when these cases come up; I'm not necessarily looking for a rule that always applies, though if there's a way to balance any rule(s) such that they can't be easily exploited (e.g- by a Wizard with a half dozen different damage types to draw on) then that'd be ideal.

Primary issue is extra die rolling.  How does Adv/Dis & other modifiers to "the next roll" work?  And it slows the game down depending on how often it comes up.

Secondary is which effects can Blast-erized?  I wouldn't let TW be focused because it's a AoE effect, but BH works (the caster is simply narrowing the cone effect). 

I definitely do like the Large Targets effect though.  It makes sense that a 10' area has twice the energy coming in compared to a 5' area.  Maybe just increase the damage & save as normal?

Quote from Jaeken>>

Primary issue is extra die rolling.  How does Adv/Dis & other modifiers to "the next roll" work?

For Directed Blast I'd assume only the first save unless an effect specifically applies to all saves for the duration (like Bane or Bless); so disadvantage/advantage on the first save would still make the target more/less likely to take the full initial damage, and therefore have to take the second save as well.

it slows the game down depending on how often it comes up.

I initially thought this as well, but would it actually slow things down much? For Directed Blast it's pretty much equivalent to if you were rolling saves for two targets; for physical and digital rolling you can roll both at the same time as long as you know which one was first (then either use or ignore the second), so I think in practice it'd still be fairly quick?

Secondary is which effects can Blast-erized?  I wouldn't let TW be focused because it's a AoE effect, but BH works (the caster is simply narrowing the cone effect).

You're probably right about dropping the special case for Thunderwave; it does feel to me like it should be eligible (as it's like Burning Hands etc. but dealing thunder damage) however having to define "a cube but only sometimes" is a little overcomplicated.

I definitely do like the Large Targets effect though.  It makes sense that a 10' area has twice the energy coming in compared to a 5' area.  Maybe just increase the damage & save as normal?

I'm not sure what you mean by increase damage & save as normal? Are you thinking to just add dice to the damage roll and/or DC based on size class? The tricky part with added dice though is how to do that consistently, as not all spells level up by only a single dice (e.g- Vitriolic Sphere) and some effects aren't spells so may not have a built-in levelling of dice?

Quote from Haravikk >>

Quote from Jaeken>>

 

I definitely do like the Large Targets effect though.  It makes sense that a 10' area has twice the energy coming in compared to a 5' area.  Maybe just increase the damage & save as normal?

I'm not sure what you mean by increase damage & save as normal? Are you thinking to just add dice to the damage roll and/or DC based on size class? The tricky part with added dice though is how to do that consistently, as not all spells level up by only a single dice (e.g- Vitriolic Sphere) and some effects aren't spells so may not have a built-in levelling of dice?

 If it would normally be 4d6 damage, make it 6d6 or 8d6 vs Large, & keep the saves to just 1 roll.

Also, have a exception for psychic damage?  Might be too cumbersome, depending on your table.