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The Drow Mage (CR 7) has the Action Summon Demon (1/day), which allows him to summon a shadow demon (CR 4). Is the shadow demon already included in the CR of the Drow Mage, or do I have to count the shadow demon as an extra creature to determine the difficulty of the encounter?

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Probably the summoned monster doesn't count toward the challenge.

Bear in mind there's no RAW that specifies this, and challenge ratings of published monsters include some degree of "eyeballing" from the writers. But we can extrapolate a bit by using the basic challenge evaluation from the DMG on the stats that we do know.

I used Monstermancer* to run the stats of the Drow Mage without the summoning ability, counting all of its spells, and came up with a baseline challenge of 7:

"eval": {
    "defCR": 0.5,
    "offCR": 15,
    "dmg": 126,
    "ac": 15,
    "hp": 45,
    "atk": 6,
    "svDC": 14
}

So, without any eyeballing or special tweaks to its challenge evaluation, the Drow Mage's challenge matches the one given in the Monster Manual (in fact, this might be a little low, since it doesn't factor in the possibility of having an ongoing cloudkill spell active while throwing lightning bolts, but I digress).

However, while it looks like the summoned creature isn't "baked in" to the summoner's challenge rating, there isn't much guidance as to how you should incorporate it into an encounter. It's less effective than a full-fledged combatant for a few reasons (it takes an action to summon, it might not always succeed, &c.), but adding a challenge 4 shadow demon to a fight against a single challenge 7 mage is not a minor impact on the encounter, so it should count for something.

For a little more circumstantial evidence, there are variants listed in the Monster Manual for demons and devils which can summon other demons and devils; there is an entry for each type of fiend and which others they can summon with a percentage chance, similar to the ability of the drow mage cited here. These variants don't mention a change to the fiends' challenge ratings. Since the book doesn't assume a difference in the creature's own challenge with or without the summon ability there, it follows that the summoned creature should count separately in some way (even if not as a full-fledged combatant).

*Caveat: Monstermancer isn't perfect at this stuff, but it's an OK starting point. Also, there's a huge mismatch between the offensive and defensive challenges it gives to the Drow Mage, so it's a lot easier to take out than its challenge rating implies.

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  • \$\begingroup\$ I think there's a difference between a full-blown creature and a summon though, right? The latter consumes an action (from a more powerful creature), always misses the first round of combat, is vulnerable to a bunch of spells (like being dismissed) and is only around for a short while. \$\endgroup\$ – Erik Oct 25 '16 at 7:30
  • \$\begingroup\$ Yeah...I'm a lot more confident in the first part of this answer (the summoned creature isn't "baked in" to the summoner's challenge) than in the second (you should count the summoned creature as a full participant in the encounter). I'll edit to make this a bit clearer. \$\endgroup\$ – Polisurgist Oct 25 '16 at 13:22
  • \$\begingroup\$ The thing about the summoned creature: The chance of actually summoning it is 50% and it will disappear, should the summoner die. A quasit could be dummoned instead, which is only CR1. I as DM wouldn't count it for as an extra creature, since you can't really say if it will be summoned or not. \$\endgroup\$ – Cédric Antunes Oct 25 '16 at 13:43
  • \$\begingroup\$ @CédricAntunes; I definitely wouldn't count it unless it was successfully summoned; I'd write up the encounter with the drow mage and retroactively note the increased challenge of the encounter (without altering the mage's challenge) if the other creature showed up. In fact, that's one reason I believe that it isn't factored into the challenge 7 that the drow already has. \$\endgroup\$ – Polisurgist Oct 26 '16 at 1:31
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I believe that the ability of being able to cast a demon once per day is already included in the Drow Mage's challenge rating.

It wouldn't make sense if a Commoner of CR 1/8 could summon a dragon and still be CR 1/8.

So... I say make it count as one creature of CR 7.


Keep in mind that a Drow Mage has very low health compared to other CR 7 creatures. The DMG (p. 274) shows a tabelle with CR 7 having around 161-175 HP and a DC of 15, while the Drow goes with 45 HP (1/3rd) and a DC of 14 (lower than normal for a spellcaster of CR 7). So I believe that the makers of this race have taken the CR in account for the demon summoning.

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    \$\begingroup\$ I think your second sentence is a false comparison: the mage in question is summoning something decently below its level, not significantly above like in your example. \$\endgroup\$ – nitsua60 Oct 24 '16 at 2:12
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    \$\begingroup\$ @nitsua60 he is referring to the idea that the cr considers the abilities, thus there is no need to adjust cr. The example exemplify that idea. It wouldn't make sense for his commoner to have a low cr if he can summon a high cr creature \$\endgroup\$ – Chepelink Oct 24 '16 at 10:51
  • \$\begingroup\$ Thanks Chepelink! Yes, I meant it as an example that the CR would have been configured to match the power... I could give a look into the DMG to see on how to create a CR and see if the Drow Mage wouldn't actually be a level lower than it normally would. \$\endgroup\$ – Cédric Antunes Oct 24 '16 at 11:10
  • \$\begingroup\$ @Chepelink he's assuming that it does, and the hypothetical example would be evidence of it. But it doesn't exist, does it? I don't have my MM with me at the moment, but I don't believe there's a CR 1/8 commoner who can summon a dragon back in the NPC section? \$\endgroup\$ – nitsua60 Oct 24 '16 at 11:45
  • \$\begingroup\$ @nitsua60 What he has to do, and I agree with you, is to prove his theory. But as far as his example goes, until evidence is shown that he is correct (or wrong) you can't say that it is wrong (or correct) \$\endgroup\$ – Chepelink Oct 24 '16 at 12:27
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The summoned creature is a separate source of XP to the Drow Mage

The Monster Manual has the following to say in the Introduction > Statistics > Challenge section:

Experience Points

[...]

Unless something tells you otherwise, a monster summoned by a spell or other magical ability is worth the XP noted in its stat block.

The Drow Mage's stat block has this to say:

Summon Demon (1/Day)

The drow magically summons a quasit, or attempts to summon a shadow demon with a 50 percent chance of success. The summoned demon appears in an unoccupied space within 60 ft of its summoner, acts as an ally of its summoner, and can't summon other demons. It remains for 10 minutes, until it or its summoner dies, or until its summoner dismisses it as an action.

As this ability doesn't tell you not to award XP for this summoned monster, the general rule from the Monster Manual applies.

The result is that you award the full XP for this monster.

These seem like strict restrictions...does that not make it easier than a vanilla shadow demon?

RAW...still no.

As a DM, however you are free to make a ruling that this applies. What follows is how I would approach such a ruling as a DM:

Where to start?

We need to do some analysis of the creature's CR. To do that analysis we will use the "Creating a Monster" portion of the Dungeon Masters Guide (DMG).

The restrictions are:

  • can't summon other demons
  • It remains for 10 minutes, until it or its summoner dies, or until its summoner dismisses it as an action.

The vanilla shadow demon cannot summon demons anyway, so the restriction on summoning is moot.

The remaining restrictions are based around how long it may last:

  • 10 minutes: The only time we really care about XP is in battle...and zero battles in D&D will last 600 rounds, so this effectively isn't a restriction (it just means shadow mages don't have a permanent shadow demon pet)
  • until it [...] dies: well if it dies that means it's been defeated and XP should be awarded for it
  • until [...] its summoner dies: This will really depend on the precise situation, as the drow mage may be at 5 HP when they try to summon the demon, or they may be at 45 HP.
  • until its summoner dismisses it as an action: in a fight this is only plausibly going to happen in two cases
    1. The summoner has won comfortably and the party failed to get any XP
    2. The summoner has been convinced to get rid of it (by force or diplomacy)

Of these possibilities there are only two that might reduce the XP award, and they are:

  • until [...] its summoner dies: This will really depend on the precise situation, as the drow mage may be at 5 HP when they try to summon the demon, or they may be at 45 HP.
  • until its summoner dismisses it as an action: in a fight this is only plausibly going to happen in two cases
    1. The summoner has been convinced to get rid of it (by force or diplomacy)

Both of these could potentially have an effect on the monsters challenge rating by altering either its Hit Points (ie the amount of HP that it still had when it disappeared due to either condition effectively reduces its total HP by that amount), or its damage output due to short time span. Both of these factors (Hit Points and Damage/Round) directly affect the CR calculation (potentially).

In the DMG section on Creating a Monster it states:

Step 8. Hit Points

[...]

Use the Table. You can start with the monster's expected challenge rating and use the Monster Statistics by Challenge Rating table to determine an appropriate number of hit points.

[...]

Step 11. Damage

[...]

Overall Damage Output

[...]

If a monster's damage output varies from round to round, calculate its damage output each round for the first three rounds of combat, and take the average.

[...]

Step 13. Special Traits, Actions, and Reactions

Some special traits (such as Magic Resistance), special actions (such as Superior Invisibility), and special reactions (such as Parry) can improve a monster’s combat effectiveness and potentially increase its challenge rating.

[...]

One thing to note, before we jump in, is that the three rounds averaging (from step 11) is in here for a reason...it strongly suggests that on average combat in D&D 5e is 3 rounds long. So let's use that as the basis.

Importantly, summoning is not listed in the list of special traits that affect CR (which gives us more evidence, if we needed it that CR of the summoned creature should be awarded on it's own).

For the effective reduction in Hit Points, we would need to figure out how many rounds after the demon is summoned, that the either condition is satisfied and the discorporation of the shadow demon occurs. Once we have that value, we need to calculate the expected HP the shadow demon would have after our expected number of rounds (less than 3!). We then subtract that value from the shadow demons HP and use the Modifying a Monster section of the DMG to appropriately adjust the Shadow Demon's Defensive CR downwards.

This damage per round figure you calculate is compared to the DMG table to figure out its offensive challenge rating. As a result, if we expect the shadow demon to last less than three rounds, due to either of these restrictions, we could calculate a new Damage/Round and adjust the Shadow Demon's Offensive CR accordingly.

Once we have made these two adjustments the average of the sum of these two CR adjustments is the CR reduction we need to apply.

Finally look up the new XP for your modified Shadow Demon and award appropriately.

So we have a possible ruling...is it worth it? Should we apply it?

In my opinion it isn't worth it (for me). It is an awful lot of work for not a huge amount of gain in the vast majority of summoned monster cases. I would, having gone through this process of coming up with a ruling just save myself the hassle of actually applying this very complicated calculation and just award the XP in the stat block.

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I think it is included

Here is why:

I used this calculator (you can also do this with the method in the book) to determine how hard this monster would be without the summon.

45 HP, 12 AC, +6 to spell attack

The most damaging spell it has (by my estimation) is lightning bolt. It may use cloudkill instead for battlefield manipulation, but LB seems to do more damage. At level 5, LB does a max of 60 damage. I called that 30 for an "average roll." Assuming it hits 2 or 3 people that becomes 60 or 90 damage in a single round.

That is not sustained damage though. Over the course of a few rounds, it will use up the spell slots, so I am guessing maybe 30-40 points of damage per round.

Using that calculator link I posted, that gives a CR of 3 or 4. Adjusting the Damage per Round, it would need to be about 90 to get to a CR 7. I don't know that it can feasibly get that amount of damage without the summon.

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  • \$\begingroup\$ I think the majority of this comes down to how many targets you think that the lightning bolt or cloudkill can hit; the big difference between your numbers on that and mine is that I'm assuming the lightning bolt can hit 4 and not 2-3 (and that I'm assuming 31.5 average damage and not 30). But you should count its AC at 15, since the challenge evaluation should assume that any spell effects that could affect that are active, and the drow mage has mage armor. \$\endgroup\$ – Polisurgist Oct 26 '16 at 1:34
  • \$\begingroup\$ This may help: rpg.stackexchange.com/q/64142/23064 \$\endgroup\$ – daze413 Oct 26 '16 at 1:47
  • \$\begingroup\$ also, the average damage of a 5-th level lightning bolt dealing 10d6 damage is 10*3.5 = 35, not 30. You can't just halve the maximum result, since that doesn't take into account that you cannot possibly roll less than 10 damage - since all of the 10 dice you're rolling will grant at least 1 damage each. \$\endgroup\$ – PixelMaster Sep 15 '18 at 23:16

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