D&D 5E How should summon spells be factored in the encounter math?

[Ondath]

So I've been delving back into 5E's fundamental math for a bit, and the summon spells (all different variations of it) have me stumped. When it comes to calculating a spell's power level, 5E's fundamental math is of some help. We know there is a certain ratio in each monster's hit points, attack bonuses, damage per round and even how special abilities like negative conditions could (with some accuracy) be translated into raw points of damage (Paul Hughes's 5e monster manual on a business card is an excellent breakdown of this ratio, and he perfected the calculations in Level Up's Monstrous Menagerie IMO). We also know, thanks to DMG p. 283-284, the amount of "raw" damage a spell should do at each spell level. Of course, 5E's own spells don't follow this chart most of the time (see Fireball, buffed to 8d6 when it should have been 6d6 as a 3rd-level spell because "it is iconic"), but there is no reason to think that the chart itself is wrong. And I think it's easy to analyse the power level of most spells just by using these two resources most of the time.

However, summon spells do not fit this mold at all. First of all, how do we measure the fact that you summon an entirely new creature to your side, with its own stack of Hit Points and a consistent damage per round? Should the summon's damage output over 3 turns be the equivalent of what a spell of same level should be? If so, none of the summon spells follow this pattern. Take Summon Fey, for instance. Most people seem to agree that the summon spells in TCE are better balanced compared to the PHB "Conjure X" spells. Summon Fey is a 3rd level spell. A 3rd level spell aimed at a single target (that is, whose damage doesn't repeat like an AoE spell) is supposed to deal 5d10 (or 27,5) points of damage in total. If the spell's total damage output should be 27,5 points of damage, perhaps we can spread that damage over 3 turns (the average length of a combat encounter), so the Fey Spirit should deal around 9 points of damage every turn. But in truth, a Fey Spirit summoned using a 3rd-level spell slot deals 13 (1d6 + 3 + 3 + 1d6) damage per turn! And this doesn't even factor in the bonus action extra ability that each kind of Fey Spirit has, which we could quantify in terms of points of damage if we wanted to. So the Fey Spirit seems to outpace the expected damage output of a 5th-level spell.

And this little calculation doesn't even consider things like the Fey Spirit's ability to soak some enemy damage due to having its own HP pool (a fact which would make its damage output much more valuable than a simple spell that deals 39 points of damage over the course of combat), or the differences in balance between other kinds of summoning spells (Conjure X, Level Up's own Conjure X variants, the can of worms that is Animate Objects...). I think one reason summon spells have such a weird space in encounter balance is because they don't seem to have been balanced for their spell level at all. If we can perhaps tune their damage output (and find a more elegant solution for the "1 player controlling multiple summons" bottleneck), then these spells would be both enjoyable, both for players and for DMs.

So, people familiar with 5E's math, how would you quantify summon spells within 5E's encounter math?

 

[aco175]

You certainly put more thought into this than myself and bring up good points. My first thoughts was that the math is built into the character and a summoned monster cannot be taken into account since it is not used by each mage or each encounter and building that factor in would be wrong. It would make some encounter harder if there is no summoned monster to fill another PC slot (basically). My campaigns do not feature that many wizards as PCs and I cannot recall any summoned monsters being used. There are other campaigns where they are in each fight I'm guessing.

I like the idea of having a summoned monster deal damage spread over a few rounds to counter the instant spells. The HP soaking effect might counter the instant damage of a fireball or such and balance out.

 

[GMMichael]

So, people familiar with 5E's math, how would you quantify summon spells within 5E's encounter math?

5e has encounter math?

(If you're still reading, thanks for the benefit of the doubt...)

Problem: calculating the difficulty of encoun...  combat encounters based solely on damage per round is like measuring the strength of an army based solely on how many bullets it has.

But here's a shot at an answer anyway: summoners should contribute to encounter math only what their non-summoning powers justify. Once a summoner brings another creature in, you need a new calculation that includes the summoned creature as a normal combatant. Who will "die" at the spell expiration. You wouldn't need a new calculation after that unless encounter math changes when normal combatants die/flee/turn their coats...

 

[Tony Vargas]

So, just, philosophically, if a monster summons other monsters, you shouldn't get exp for defeating the extra monster that was summoned, and they shouldn't count towards the difficulty of the encounter, as the summoning is already accounted for in the value of the original monster.

If the summoning is a spell, ideally, all you should need is the level of the spell to understand what it adds to CR, because spells of the same level should have comparable value, each in the situation it's most useful. Otherwise, the spell is over or under powered.

Of course, neither spells nor monsters are that precisely designed, and the other side of the encounter equation, the party, is equally borked because class balance in non existent.

Sorry to go over that only to be defeatist & pessimistic, but the point is you're worrying over a degree of CR accuracy that doesn't exist in the game, and would be useless even if it did.

DMing is not a plug in the numbers exercise, it's an art. You can do it by feel. You can color as far outside the guidelines as you want and you can erase some of it if you go too far.

By all means, use CR like every other element of D&D, as a convenient starting point. Them adjust as you go.

Thanks for putting up with the Grognard rambling, as a bonus:

If you're creating a monster and want it to summon things, dont give it a summon spell and try to recalculate it's CR, add the summoned monsters to the encounter. Treat it like any other wave encounter.

What? That's exactly the opposite of what I said at the start?
Yes, yes it is.
Such is the way of the DM.

 

[Quickleaf]

None of these maths are "perfect" because you'll need to make guesstimates about how the scenario will play out. And the map is not the terrain. So armed with the knowledge that YMMV, here's the approach I would take...

Let's say this monster casting 3rd level Summon Fey has (a) only very few spells with concentration, (b) begins the combat >60 feet from the PCs, and (c) is supported by some kind of defense whether cover, force field, Shield spell, or henchmen/allies.

Because of these factors, I'll assume that it maintains Concentration on Summon Fey for 2 rounds, instead of just 1 round (which is my baseline assumption). When the Concentration ends? Bye bye spirit.

Note that if the monster has Constitution save proficiency and/or Mirror Image in addition to some of my points above? Definitely consider assuming it maintains Concentration for 3 rounds.

So I just factor in 2 * 13 = 26... I factor 26 damage into the monster's DPR calculation (which is calculated as a 3-round average).

And that's going to get you pretty close.

 

[Incenjucar]

A simple method is to lie.

The "summoner" is actually something else, and the summons are standard extraplanar monsters, and you just say "they use their forbidden power to summon a horde of monsters" while knowing it's actually just a bunch of monsters plus a bard

 

[Ondath]

5e has encounter math?

(If you're still reading, thanks for the benefit of the doubt...)

Problem: calculating the difficulty of encoun...  combat encounters based solely on damage per round is like measuring the strength of an army based solely on how many bullets it has.

But here's a shot at an answer anyway: summoners should contribute to encounter math only what their non-summoning powers justify. Once a summoner brings another creature in, you need a new calculation that includes the summoned creature as a normal combatant. Who will "die" at the spell expiration. You wouldn't need a new calculation after that unless encounter math changes when normal combatants die/flee/turn their coats...

I mean, you're not wrong about 5E not having an encounter math... But I did backport Level Up's encounter math to 5E

I did consider the idea about counting summons as a new monster (essentially like temporary sidekicks), but that bothers me in a different way. If there are guides on how to account for balance when an encounter has waves (or where some creatures come in and out mid-encounter), that could be useful. But as @Tony Vargas says, the main comparison for summon spells should be with other spells of equal spell level. Otherwise it feels a bit like apples and oranges. And none of the other spells need to be factored in like a combatant.

So, just, philosophically, if a monster summons other monsters, you shouldn't get exp for defeating the extra monster that was summoned, and they shouldn't count towards the difficulty of the encounter, as the summoning is already accounted for in the value of the original monster.

If the summoning is a spell, ideally, all you should need is the level of the spell to understand what it adds to CR, because spells of the same level should have comparable value, each in the situation it's most useful. Otherwise, the spell is over or under powered.

Of course, neither spells nor monsters are that precisely designed, and the other side of the encounter equation, the party, is equally borked because class balance in non existent.

Sorry to go over that only to be defeatist & pessimistic, but the point is you're worrying over a degree of CR accuracy that doesn't exist in the game, and would be useless even if it did.

DMing is not a plug in the numbers exercise, it's an art. You can do it by feel. You can color as far outside the guidelines as you want and you can erase some of it if you go too far.

By all means, use CR like every other element of D&D, as a convenient starting point. Them adjust as you go.

Thanks for putting up with the Grognard rambling, as a bonus:

If you're creating a monster and want it to summon things, dont give it a summon spell and try to recalculate it's CR, add the summoned monsters to the encounter. Treat it like any other wave encounter.

What? That's exactly the opposite of what I said at the start?
Yes, yes it is.
Such is the way of the DM.

You've summed up the debate I had in my mind while I typed the post! My main concern isn't actually with NPCs using summoning spells (which is related to @Incenjucar's advice as well), but with players using those spells.

More specifically, I started thinking when I considered Animate Objects (both its 5E and Level Up A5E version). If you animate Tiny objects, the 5E version deals way too much damage. The A5E version nerfed the spell for this reason, but I think they went too far in the other direction: Now the tiny swarm option is a joke for what is supposed to be a 5th-level spell. Then I tried to run some calculations to see how I could rebalance the spell, which led me to think about other summon spells in general, which then led to this thread...

I know there really can't be a perfect mathematical equation for making sure all spells and encounters deal the perfect amount of damage. But surely I think to myself, surely somebody had some logic in their minds when they were assigning these numbers (summoned monster HP, AC, damage per round etc.) while writing these spells... It remains to be seen if this is indeed the case.

None of these maths are "perfect" because you'll need to make guesstimates about how the scenario will play out. And the map is not the terrain. So armed with the knowledge that YMMV, here's the approach I would take...

Let's say this monster casting 3rd level Summon Fey has (a) only very few spells with concentration, (b) begins the combat >60 feet from the PCs, and (c) is supported by some kind of defense whether cover, force field, Shield spell, or henchmen/allies.

Because of these factors, I'll assume that it maintains Concentration on Summon Fey for 2 rounds, instead of just 1 round (which is my baseline assumption). When the Concentration ends? Bye bye spirit.

Note that if the monster has Constitution save proficiency and/or Mirror Image in addition to some of my points above? Definitely consider assuming it maintains Concentration for 3 rounds.

So I just factor in 2 * 13 = 26... I factor 26 damage into the monster's DPR calculation (which is calculated as a 3-round average).

And that's going to get you pretty close.

Hm, so perhaps it makes more sense to calculate the summon spells' power level by assuming that the summon won't stay for the whole combat, but two turns? That actually makes sense. I think A5E Monstrous Menagerie says you should consider that any ongoing damage dealt by a monster is dealt for one turn and then ends. So the summon being able to stay for two rounds could be something similar.

But that still leaves the other numbers a mystery. Why does A5E's Conjure Elemental summon a creature with 60 HP? Are the HP and AC tied to the summoned monster's damage capabilities (as it would be the case if this was a proper monster designed with the CR guidelines)? I'll try and continue this idea to see if it leads somewhere!

 

[Incenjucar]

A summon's defenses only really come into play if they're low enough to be taken out quickly in combat, otherwise it functions like any other ongoing spell effect.

 

[FrogReaver]

Feels kind of like trying to balance fireball when it can hit 1 to 10+ enemies.

Instead you look at the average case. Fireball hits 3 enemies. Summon Fey attacks for 3 rounds.

Of course spells gain power if you pick the right spell for the right job. Fireball when you can hit 4+ enemies. Summon fey when it will last 4+ rounds. Etc.

Which is why wizards tend to be OP. They balance around the average case but you use only on better than average cases.