# How do I determine Shadow Dragon's Breath Save DC?

From the Shadow Dragon template, it would appear that the Shadow Breath has the same damage and save as the original dragon's breath weapon, as no change is stated in the template:

New Action: Shadow Breath. Any damage-dealing breath weapon possessed by the dragon deals necrotic damage instead of its original damage type. A humanoid reduced to 0 hit points by this damage dies, and an undead shadow rises from its corpse and acts immediately after the dragon in the initiative count. The shadow is under the dragon's control.

However, analyzing the provided example of applying the template to a Young Red Dragon (whose Breath Weapon has a DC of 17), the Young Red Shadow Dragon has a Shadow Breath with DC 18.

Am I missing something? If the DC was kept at 17, would it lead to a different CR? In that case, what comes first: The CR or the DC?

• The CR is actually quite different as well. CR 10 for the young red dragon, CR 13 for the young red shadow different. Would make sense for it to be slightly higher given the extra abilities, but +3 difference seems a bit much and the template doesn't mention a CR change.
– PJRZ
Aug 10 '19 at 16:20
• @PJRZ rpg.stackexchange.com/q/139180/43856 - that's answered here. The increase in CR comes from the resistances the shadow dragon gets while in dim light or darkness. Aug 10 '19 at 16:34

The young red shadow dragon is a CR 13 monster. A young red dragon is CR 10.

According to Dungeon Master's Guide page 274, under the heading "Creating Quick Monster Stats", the proficiency bonus for CR 10 is 4, and for CR 13 is 5. Since both dragons have the same ability scores, I suggest that the 1 DC difference is caused by this.

I went through some (not all) dragon statblocks to see if there is a pattern for their breath weapon DC, taking into account the standard DC calculation formula of 8 + prof. bonus + ability modifier.

Based on my research, the DC is likely based on the dragon's Constitution score.

• Blue Dragon Wyrmling: CR 3, Con 2, Prof 2, DC 12, 8+2+2 = 12
• Young Green Dragon: CR 8, Con 3, Prof 3, DC 14, 8+3+3 = 14
• Adult White Dragon: CR 13, Con 6, Prof 5, DC 19, 8+6+5 = 19
• Adult Gold Dragon: CR 17, Con 7, Prof 6, DC 21, 8+7+6 = 21
• Ancient Bronze Dragon: CR 22, Con 8, Prof 7, DC 23, 8+8+7 = 23

For the red dragons, we have:

• Young Red Dragon: CR 10, Con 5, Prof 4, DC 17, 8+5+4 = 17
• Young Shadow Red Dragon: CR 13, Con 5, Prof 5, DC 18, 8+5+5 = 18

As for what comes first, DC or CR: Since the shadow dragon uses the statblock of the original dragon and then gains some new traits, first I would adjust the dragon's CR by the new traits - and then if its proficiency bonus changes because of the CR change, I suggest to go back and adjust the values that require the proficiency bonus accordingly.

Related questions

• Actually the DC for CR10 monsters is 16. Which is another reason the change in the DC seems awkward for me - it didn't follow the table to begin with. The other problem is that this enters into a loop question: how do you determine the CR for the Shadow Dragon, if its statistics (such as the DC, but maybe AC, to hit, etc.) may also change depending on the final CR? See rpg.stackexchange.com/q/139180/43856 for related question. Aug 15 '19 at 0:21
• @HellSaint You are right. My bad. I went through DMG again and it seems however that the DC might be based on the dragon's CON bonus. I will edit the answer accordingly. Aug 15 '19 at 7:23