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I am homebrewing a monster that has incorporates the Swallow mechanic used by the Behir (MM, pg. 25). My monster is not at the same CR and I need to adjust its statistics accordingly, but there is one part of Swallow's text:

... the behir must succeed on a DC 14 Constitution saving throw at the end of that turn or regurgitate the creature.

How is the 14 DC calculated? Is there some formula to arrive at 14, as opposed to 17 or 12? Or is it less rigorous than that and more subjective?

NathanS
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A Random Guy
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1 Answers1

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I think the DC is just 10 + the CON save modifier of the creature. The Remorhaz has a similar mechanic and the save for it is DC 15 and it has a CON modifier of +5.

As mentioned by Revolver_Ocelot in the comments, the Kraken has a CON save modifier of 15 even though it's CON modifier is only +7. The DC for it's swallow ability is 25. Oddly enough it's CON save modifier in the SRD is only 14 even though it is 15 in the Monster Manual.

Allan Mills
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    It is interesting to note that the giant toad also has a "swallow" feature but it has no con save to regurgitate swallowed creatures. But I agree with this answer as the DC for the Tarrasque's swallow is 20 and it has +10 CON – Karan Shishoo Jan 07 '20 at 04:32
  • It's interesting how this is different from how PCs derive save DCs, which is usually 8 + proficiency bonus + ability modifier, whereas these monsters all appear to use 10 + ability modifier; you would think they'd keep the same formula, which would take the proficiency bonus into account... especially since the DC for the various different dragons' breath weapons do calculate the DCs in the same way as PCs do! The designers must have decided that swallow is somehow inherently different from, say, a dragon's breath weapon. – NathanS Jan 07 '20 at 11:22
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    @NathanS the distinction is that this is a saving throw that the creature is making in order to keep its lunch down, as opposed to the save that a target is making to avoid an effect! The DC appears to be calculated in such a way as to always give them a roughly even (55:45) chance of succeeding, since a monster's normal con save bonus would just be it's con modifier, so setting the DC at 10+con mod cancels them out. The DMG's guide to creating monsters does specify setting save DCs for effects at 8+prof+mod as is usual in the system, swallow self-save DCs are an understandable exception. – Carcer Jan 07 '20 at 13:08
  • @Carcer Ah, that does explain it. Thanks for the info! – NathanS Jan 07 '20 at 13:48
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    That calculation doesn't seem to always work. The Gelatinous Cube has two save DC's. Strength 12 and Dexterity 12 with a Strength mod of +2 but a Dexterity mod of -4. The Banshee has a Wisdom and Constitution save of 13 with a Wisdom mod and Constitution mod of +0 and a proficiency bonus of +2. – Eternallord66 Jan 07 '20 at 14:24
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    @Eternallord66 the ability score used to determine a DC isn't necessarily the same as the ability score used to save against it - a Wizard determines all their spell save DCs based on intelligence, but it's the spell that determines the ability used for the saving throw. The DC for the gelatinous cube's abilities appear to be based on the cube's Strength and the Banshee's are based on her Charisma. – Carcer Jan 07 '20 at 14:48
  • More precisely it is 10 + constitution saving throw modifier. Kraken has +7 CON modifier, but +15 CON saving throw modifier. And keep lunch DC is 25. – Revolver_Ocelot Jan 07 '20 at 18:31
  • ... And Volo messed it all up. It makes DC for creatures published here higher, so it is harder for them to keep PC inside... – Revolver_Ocelot Jan 07 '20 at 18:38
  • @Revolver_Ocelot Good point. I'll modify my answer. – Allan Mills Jan 07 '20 at 19:35
  • The kraken's Con save modifier is +14. The MM errata notes this change at least as of 2016, so the MM statblock matches the one in the SRD as well. – V2Blast Jan 08 '20 at 08:06
  • @V2Blast Hmm, then that means the save DC for the kraken's swallow ability has an extra +1 for no good reason. Presumably they forgot to errata that as well. – Allan Mills Jan 08 '20 at 19:41