False Hydra 5e: Stat Block, Clues & How to Run It (Complete DM Guide)

The False Hydra is not in any official Monster Manual. It was invented in a 2014 blog post, spread through forums and actual-plays, and has since become the most-shared, most-feared, and most-badly-run homebrew monster in Dungeons & Dragons. The idea is simple and awful: a pale, eyeless, many-necked thing lives under a town and sings. Anyone who hears the song cannot perceive the creature and cannot remember the people it eats. The town empties one neighbour at a time, and nobody notices.

This guide gives you everything the original post deliberately left out: a complete 5e stat block with numbers, a table of clues you can drop into any town, a four-act structure that keeps the twist earned rather than cheap, and the mistakes that turn a slow-burn horror story into a "gotcha". If you only want the stats, they are right below.

False Hydra 5e Stat Block (CR 7)

There is no canonical stat block. This one is tuned for a party of four at levels 5–7 and built so the song does the work, not the hit points. Scaling notes follow the block.

False Hydra
Huge aberration, unaligned
Armor Class	15 (natural armour)
Hit Points	142 (15d12 + 45)
Speed	20 ft., burrow 20 ft.
STR / DEX / CON	20 (+5) / 10 (+0) / 17 (+3)
INT / WIS / CHA	8 (−1) / 14 (+2) / 18 (+4)
Saving Throws	Con +6, Wis +5, Cha +7
Skills	Perception +5, Stealth +6 (+12 while singing)
Damage Resistances	Bludgeoning, piercing and slashing from non-magical attacks
Condition Immunities	Charmed, frightened, prone
Senses	Blindsight 60 ft. (blind beyond this radius), passive Perception 15
Languages	Understands Common and Deep Speech but cannot speak; mimics voices (see Mimicry)
Challenge	7 (2,900 XP)
Proficiency Bonus	+3

Traits

• Mindsong. While the false hydra sings (a free action it can sustain indefinitely, even while attacking), every creature within 1 mile that can hear it is affected. Affected creatures cannot perceive the false hydra by any sense, cannot remember any creature the false hydra has killed, and rationalise any evidence of either. Creatures that are deafened, under the effect of mind blank, or inside a silence spell are unaffected while the condition lasts. A creature that leaves the 1-mile radius regains its memories after 1d4 hours, and loses them again 1 minute after re-entering. Undead, constructs and creatures with an Intelligence of 3 or lower are immune.
• Song of Silence. Casting a spell with a verbal component, or making a Charisma (Performance) check to sing louder than the hydra, does not stop the song. Only killing the hydra, deafening it, or moving it more than 1 mile from a creature ends the effect for that creature.
• Multiple Heads. The false hydra has 1d4 + 2 heads (roll once). While it has more than one head, it has advantage on saving throws against being blinded, deafened, stunned and knocked unconscious. Whenever it takes 25 or more damage in a single turn, one of its heads dies. If all heads die, the false hydra dies.
• Regrowth. At the end of its turn, if the false hydra has at least one head and took no fire or acid damage since its last turn, it grows one new head for each head that died since its last turn, and regains 10 hit points per head regrown. A dead head does not regrow if the stump was burned or dissolved.
• Mimicry. The false hydra can mimic any voice it has heard. A creature that hears the mimicry can tell it is an imitation with a successful DC 15 Wisdom (Insight) check, but only if it is not affected by Mindsong.
• Tunneller. The false hydra can burrow through worked stone and packed earth at half its burrow speed, leaving a 5-foot-wide tunnel.

Actions

• Multiattack. The false hydra makes as many bite attacks as it has heads.
• Bite. Melee Weapon Attack: +8 to hit, reach 15 ft., one target. Hit: 12 (2d6 + 5) piercing damage. If the target is a Medium or smaller creature, it is grappled (escape DC 16). Until this grapple ends, the target is restrained, and the head cannot bite another target.
• Swallow. The false hydra makes one bite attack against a Medium or smaller creature it is grappling. If the attack hits, the target takes the bite's damage, is swallowed, and the grapple ends. A swallowed creature is blinded and restrained, has total cover against attacks from outside, and takes 14 (4d6) acid damage at the start of each of the hydra's turns. If the hydra takes 20 or more damage in a single turn from a creature inside it, it must succeed on a DC 15 Constitution saving throw or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of it. A creature that dies inside the hydra is erased from the memory of everyone under the Mindsong.
• Lure (Recharge 5–6). One head mimics the voice of a creature the target knows. One creature within 60 feet that can hear it must succeed on a DC 15 Wisdom saving throw or use its reaction to move up to its speed toward the sound by the safest available route.

Legendary Actions

The false hydra can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature's turn. It regains spent legendary actions at the start of its turn.

• Bite. The false hydra makes one bite attack.
• Withdraw (Costs 2 Actions). The false hydra burrows up to its burrow speed without provoking opportunity attacks. Creatures affected by Mindsong lose track of it immediately.
• Swell the Song (Costs 3 Actions). Every creature within 60 feet that is not affected by Mindsong must succeed on a DC 15 Wisdom saving throw or become affected by it until the end of its next turn.

Scaling the False Hydra

Party	Heads	HP	Bite	Changes
Levels 3–4	2	85	+6, 9 (1d8 + 5)	No legendary actions, no resistances, Swallow DC 13. CR 4.
Levels 5–7	1d4 + 2	142	+8, 12 (2d6 + 5)	As written. CR 7.
Levels 8–11	6	210	+10, 16 (2d10 + 5)	Add Legendary Resistance (2/day), Mindsong DC 17, Swallow acid 21 (6d6). CR 11.
Levels 12+	7+	270	+11, 21 (3d10 + 5)	Song radius 5 miles; townsfolk act as thralls (use cultist stats, advantage on attacks against creatures the hydra has bitten). CR 14.

The CR is honest for the fight only. The real difficulty is the investigation, and that is deliberately not on the stat block.

What Is a False Hydra?

A false hydra is a pale, wet, hairless mass of flesh with a body somewhere between an alligator and a drowned man, and anywhere from two to a dozen necks that end in distorted human heads. It has no eyes; the sockets weep. It lives in the dark under an inhabited place — a cellar it has hollowed out, a dry cistern, the crypt under the chapel — and it grows one foot longer for every person it eats.

It sings. The song is not loud. It is closer to a hum you would only notice if it stopped. Anyone who hears it cannot perceive the hydra and cannot remember anyone the hydra has eaten. The townsfolk aren't lying when they say the baker never had a wife. They are telling you the only truth their minds will permit.

The horror is not the monster. It is the town: a place that seems ordinary in every way except that it has too many empty chairs and nobody can say why.

The Mindsong: Running the Memory Mechanic

Everything about the false hydra hangs on this, so run it precisely. Three rules keep it fair:

1. The song affects characters, not players. Players will notice the clues. Their characters cannot act on the ones the song covers. The tension between what the table knows and what the sheet can do is the game. Say this out loud in session zero for the arc: "Your characters may not be able to remember things you remember. That's the monster, not me cheating."
2. The song hides the hydra and its victims. Nothing else. Blood on the floor is visible. An unlit lamp that someone should have lit is visible. A letter that says "help me" in a stranger's hand is visible. The characters see the evidence; they cannot form the conclusion. Let them collect the evidence anyway. When the song breaks, it all snaps into place.
3. Breaking the song is the climax, not the start. The party should discover how the song works (deafness, silence, distance) two-thirds of the way through the arc, and choose to use it. The moment they stop their ears and see the thing for the first time is the scene the whole arc exists for.

Mechanically: don't call for saves. Mindsong has no save on purpose. The way out is to change the conditions — deafen yourself, cast silence, walk a mile out of town — and that is a decision, not a roll.

False Hydra Clue Table

Drop one clue per in-game day, or roll a d12 when the party pokes at something. Each row is something the characters can perceive; the conclusion is what they can't reach.

d12	What the party notices	What it means
1	A dining table set for six. Four people live here. Nobody can say why they own six chairs.	Two eaten.
2	A child's shoes by the door of a couple who insist they have no children.	The child was first.
3	The tavern's ledger has a regular tab, paid weekly, in a name nobody recognises. The last entry was three days ago.	Eaten mid-week.
4	Every dog in town is fine. Every cat has left.	Cats hear it. Dogs don't mind.
5	A half-finished job: a wall two-thirds painted, ladder still against it, brush dried in the pot.	The painter was taken off the ladder.
6	The priest's sermon list names a mourner for a funeral that, he says, never happened.	The funeral happened. The body was eaten afterwards.
7	A letter arrives for the party from the town, sent a week ago. The last line, in a different hand: "please, there is something".	The classic hook. The writer is gone.
8	Grain stores are stocked for twice the current population.	The population used to be twice this.
9	A mirror in the inn's corridor shows, for a second, a long white neck through the window. Nobody else looked.	Mirrors show what the mind won't.
10	The cobbler greets the party warmly, then asks their names again a minute later. His hands shake.	Someone whose mind is fraying under the song.
11	Fresh blood on the cellar stairs. The innkeeper sees it, frowns, and mops it without comment.	He can see blood. He cannot ask why.
12	A voice calls a party member by name from the well. It is a voice they know. That person is standing beside them.	Lure. The hydra has learned their names.

Running a False Hydra Arc in Four Acts

Three to five sessions is the sweet spot. Shorter and the horror has no room to breathe; longer and players start resenting the mechanic.

Act 1 — The Hook (1 session)

The party arrives for an unrelated reason: a delivery, a festival, a rumour of work. Use the letter (clue 7) or a patron who wants a missing person found — a person who, once the party gets there, nobody has heard of. Plant two clues from the table. Let the town be pleasant. End on something small and wrong.

Act 2 — The Wrongness (1–2 sessions)

Clues every day. A frayed townsperson (clue 10) who is starting to break. A red herring: give the town a real, mundane secret — smuggling, an affair, a debt — so the party has something to solve while the real thing keeps eating. Have an NPC the party liked disappear between sessions; when they ask, nobody knows who they mean. If a player says "that's a false hydra", smile and say nothing. Their character still can't remember.

Act 3 — The Discovery (1 session)

The party learns the rule. Options: a deaf beggar who alone remembers everyone, and is treated as mad; a sage's note about the "song under the town"; a character who leaves on an errand and, a mile out, remembers everything at once and sprints back. The party now knows what it is and how to see it. Let them plan. The plan should be theirs.

Act 4 — The Reveal and the Fight (1 session)

Wax in the ears, silence on the cellar door, or an hour's march out and back with cotton wadding — however they do it, the first time they see the hydra should be described slowly. Then run the fight from the stat block, in the tunnels, with heads coming through walls. When it dies, the song stops for the whole town at once. Describe that: a hundred people remembering a hundred dead in the same second. That is the ending. Don't rush it.

Common Mistakes When Running a False Hydra

• Erasing the players' memories. Telling players "you don't remember that" about things they wrote down. The song erases the characters' memory of victims; it doesn't erase notes, and it doesn't erase the players. Rule the characters, not the table.
• Springing it in one session. The reveal only lands if the town felt real first. If you don't have three sessions, run a different monster.
• Making it a fight. The stat block above is fine, but a party that finds the cellar in session one and rolls initiative has skipped the monster. Keep it burrowed and singing until Act 4.
• No exit. Every act needs a way to make progress. If the party is stuck, a townsperson breaks (clue 10) and says something true before the song reasserts itself.
• Killing PCs off-screen. A swallowed PC who dies inside the hydra is a devastating beat precisely because the others forget them. Use it once, with a player who's in on it, or not at all.

Variations

• The Choir. Two hydras in neighbouring towns whose songs overlap on the road between. Travellers forget where they were going.
• The Lord's Hydra. The local noble knows, and feeds it prisoners in exchange for the town forgetting his crimes. The hydra is the cover-up.
• The Kind Hydra. It eats only the dying and the grieving, and the town is, genuinely, happier. The party has to decide whether to break it.
• Urban. Under a city ward, with a song radius of a few streets. The ward is a hole in the city's memory; the city guard has no record of it on any map.

Frequently Asked Questions

Is the False Hydra an official D&D monster?

No. It is homebrew, created in a 2014 blog post, and has never appeared in an official Wizards of the Coast book. Any stat block, including this one, is a community version.

What CR is a False Hydra?

Whatever you need. The block above is CR 7 for a level 5–7 party, with scaling to CR 4 and CR 14. Its true difficulty is the investigation, which CR doesn't measure.

How do you see a False Hydra?

Stop hearing the song: deafen yourself (wax, a deafness spell), stand inside a silence spell, or move more than a mile away. Mirrors also reflect the hydra, which is why a glimpse in a mirror is a classic clue.

Can you kill a False Hydra?

Yes. Kill every head, and burn or dissolve the stumps so they don't regrow. Once it dies, the song ends for everyone at once and every memory it erased comes back.

What level should the party be for a False Hydra?

Levels 5 to 8 is ideal: strong enough to survive the fight, low enough that mind blank and easy teleportation aren't on the table. Use the scaling table for other tiers.

How long should a False Hydra arc last?

Three to five sessions. One session isn't enough for the town to feel real; more than five and the memory mechanic starts to frustrate players rather than frighten them.

Tools for Your False Hydra Town

A false hydra town needs to feel populated, which means named people with jobs and habits. Roll a dozen with the NPC Generator, give the inn a name and a menu with the Tavern Generator, and use the NPC Stat Block Generator for the guards who will, eventually, have to fight beside the party. If you're balancing the Act 4 fight against extra threats, the Encounter Builder will tell you what a CR 7 hydra plus thralls does to your party's action economy. For more slow-burn arcs, our 50 campaign plot hooks has a horror section.