Elemental Nature. The hydra does not need to sleep, eat, or breathe.
Illumination. The hydra sheds bright light in a 60-foot radius and dim light in an additional 60 feet.
Magma Form. The hydra can move through a space as narrow as 1 foot wide without squeezing. A creature that touches the hydra or hits it with a melee attack while within 5 feet of it takes 11 (2d10) fire damage. In addition, the hydra can enter a hostile creature's space and stop there. The first time it enters a creature's space on a turn, that creature takes 11 (2d10) fire damage and catches fire; until someone takes an action to douse the fire, the creature takes 5 (1d10) fire damage at the start of each of its turns.
Multiple Heads. The hydra has twelve heads. While it has more than one head, the hydra has advantage on saving throws against being blinded, charmed, deafened, frightened, stunned, and knocked unconscious.
Whenever the hydra takes 30 or more damage in a single turn, one of its heads dies. If all its heads die, the hydra dies. At the end of its turn, it grows two heads for each of its heads that died since its last turn, unless it has taken at least 30 points of cold damage since its last turn. The hydra regains 25 hit points for each head regrown in this way.
If it has more or fewer than twelve heads when it completes a long rest, it returns to having twelve heads.
Reactive Heads. For each head the hydra has beyond one, it gets an extra reaction that can be used only for opportunity attacks.
Limited Water Susceptibility. For every 50 feet the hydra moves in water, or for every 50 gallons of water splashed on it, it takes 1 cold damage.
Multiattack. The hydra makes as many slam attacks as it has heads, and can then create new heads.
Slam. Melee Weapon Attack: +11 to hit, reach 20 ft., one target. Hit: 11 (1d10 + 6) bludgeoning damage plus 16 (3d10) fire damage.
Create Head. The hydra can create up to six new heads. It loses 25 hit points for each head it creates in this way.
Pyroclastic Annihilation. If the hydra has more than 1 head, it can destroy as many of its remaining heads as it wants to create an eruption of magma and volcanic gas that rapidly cools into stone. Each creature within 90 feet of the hydra must make a DC 17 Dexterity saving throw. On a failure, the creature takes 2d10 fire damage plus 2d10 poison damage for each head the hydra destroyed, and is restrained. It takes half as much damage and is not restrained on a successful one.
A creature restrained in this way takes 22 (4d10) fire damage at the start of each of its turns, and can make a DC 17 Strength saving throw as an action to break out of the cooling magma, ending the effect on itself on a success.
Description
The pyrohydra is a hulking serpent of pure magma with a dozen flailing heads. Born of divine elemental power, this living pyroclastic flow leaves a trail of oozing, burning destruction wherever it moves. Its heads are amorphous extensions of its own elemental nature. Like other hydras, it can grow more heads whenever one of its existing heads is destroyed—however, it can also channel its own elemental life force into creating new heads.
Just curious, is there a particular reason the pyrohydra is gargantuan, rather than huge? Is it simply because of the higher CR?
The reason it's Gargantuan is because it's essentially a living pyroclastic floe, and thus much larger than a regular hydra.
very cool, i like this one much more then the cyrohydra
Ooh, this looks like fun :) Quick clarification question: Is 1) or 2) correct?
1) On a failure, the creature takes (2d10 fire damage plus 2d10 poison damage) for each head the hydra destroyed, and is restrained.
2) On a failure, the creature takes 2d10 fire damage (plus 2d10 poison damage for each head the hydra destroyed), and is restrained.
I suspect 1) is correct, but I would like to make sure. Some of my setting's backstory has to do with ancient elementals, so I will almost definitely be using this!
Your first reading is correct!
I think there is a typo - "breath" should have an "e" at the end of "does not need to eat, sleep, or breath."
The Water Susceptibility trait causes this to get one-shot by a 3rd level tidal wave spell which can turn it into a CR 1 creature if the PC has a good enough initiative roll.
I suggest either replacing it with Cold Damage Vulnerability, capping the Susceptibility damage, or just removing the trait all together.
Love this overall though; I'll be using the stat block tonight as a weakened version of Maegera in Gauntlgrym!
That is actually true. The entire spell could hit the Pyrohydra seeing as it is a Gargantuan creature. Rougly 7.48 gallons of water fit in one cubic foot, so if the size of Tidal Wave is 30 feet by 10 feet, thats 300 cubic feet. This means that the Pyrohydra would take 2,244 cold damage from one low level spell. This does make any water spells very powerful against the creature. I agree that perhaps it should be modified a bit.
Thanks for the feedback, everyone! To limit the power of water against this creature, I've modified its Water Susceptibility trait to:
Limited Water Susceptibility. For every 50 feet the hydra moves in water, or for every 50 gallons of water splashed on it, it takes 1 cold damage.
This is one of the coolest monsters I've ever seen.
What’s to stop the Pyrohydra from detonating 11 heads for 22d10 fire and 22d10 poison damage in the first turn? Does the hydra take damage from using the pyroclastic annihilation?
The create heads feature should lower the hydras maximum HP, or that could get out of hand very very quickly. Especially considering long rests exist
Minor note:
I noticed there isn't an average number listed with the fire and poison damage. The restrained condition on being covered in magma does not have a link to the tooltip
The damage numbers here seem a bit high.
Pyroclastic Annihilation
Say the pyrohydra roles high in initiative, the party all within 90 feet, it has not taken 30 cold damage yet. All damage is average
11 heads go pop, every party member within 90 feet fails their save! Each party member takes 121 fire and 121 poison damage, and is restrained, taking an additional 22 fire damage at the start of their turn. Assuming a party of 4 all within 90 feet of the pyrohydra, that is 1056 total damage round one.
Oh, and at the end of the pyrohydra's turn, since it lost 11 heads since its last turn, it grows 22 new heads. Everyone who is restrained will have a harder time succeeding against the next-likely larger-explosion.
So some thoughts on this. The expected average damage per round of a CR 30 monster from the DMG is 303-320. If the pyrohydra makes no more attacks for 2 more rounds, they sit significantly above that category. That's a lot of damage, and gets around a hydras big weakness to failing a save against Slow.
Possible solutions:
Now, maybe the pyrohydra just doesn't have that ability to make its heads explode.
More heads to slam with my dear
It enters the fighters space: dealing 11 fire damage.
The fighter is on fire: 5 fire damage.
The fighter is attacked by 12 heads: 132 bludgeoning damage plus 192 fire damage.
Total for 1 round assuming no attacks of opportunity and that no one attacks the pyrohydra: 340 damage(11+5+132+192)
Closing thoughts
Looks really hot, and I'm probably going to use a variant of this for a final encounter in a firenewt village.
Just checking math - in terms of CR - this does, RAW, 12 x 27 damage attacks at +11 with a big body to support that damage.
I would, shooting from the hip, CR it way higher than 13. With 20' reach this thing could drop several party members in one go if they didn't resist fire.
It's immune to several damage types; am I missing something re it being CR 13?
I think the basic solution to all of this is just changing the head regrowth to the beginning of the pyrohydra's turn rather than the end.
Blowing 11 heads for Pyroclastic Annihilation may wipe the whole party, but, if it doesn't, then the pyrohydra is down to 5HP at the end of its turn and a farmer with a shortbow and 11 feet of movement could take it out.
@JamesHaeck Love, love, love the three hydra set. Tuning in to the comments and trying to make edits because it's so good. I'd love to see these in the next MTG/Theros book.
Ohhhh I can't wait to see how my high-level group deals with one of these guys.....
Couldn't agree more. These are challenging even to a very powerful group of characters, and any amount of player experience, if the DM is clever.
Looking forward to more in this series!!
the problem is that pyroclastic annihilation does not have an hp cost, unless it also takes the poison damage from its explosions, which is still rather negligible in my opinion. although it does limit the amount of heads it can explode (if it sacrifices 11 of its 12 heads and takes 30 damage it dies even though it only lost 30 hp) which is great
Um... for Pyroclastic Annihilation, it does not show the average damage for the 2d10 Poison and Fire damage. I assume this is a typo..?