Why the False Hydra is D&D’s best homebrew monster — and why you can only run it once

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I have been playing Dungeons & Dragons for more than 20 years, and in all that time, I have never encountered a monster more original and interesting than the False Hydra. Perhaps the most popular homebrew creature of all time, the False Hydra was created in 2014 by Arnold Kemp and published on his blog, Goblin Punch. As I was looking for ideas for a short adventure to run for my regular group, I stumbled upon this fearsome creature and decided to subject my players to the horror that is the False Hydra.

What makes it so compelling? No one knows it’s there. The False Hydra’s song generates an inattentional blindness effect: Every creature who hears it (usually in a five-mile radius) fails to perceive the monster, even if it’s right in front of them, ready to feast. Moreover, this twisted protection system extends to the victims of the False Hydra. Any creature devoured by the beast will be forgotten, erased from the memory of the songs’ victims. Add to this a creepy aesthetic inspired by the most disturbing creature in The Legend of Zelda: Ocarina of Time, and the False Hydra’s habit of infiltrating quiet, remote villages, and you’ve got all the elements for a great horror adventure — something that’s not easy to pull off in D&D’s high-power fantasy context.

Running a False Hydra offers a DM endless opportunities for clever, memorable, and sometimes truly chilling story bits. For my adventure, I admit to borrowing a lot of them from this video from another amazing creator, The Toast Thief. I won’t spoil it in case readers will find themselves in a False Hydra adventure someday, but let me just say that messing with characters’ memories is one of the most interesting things that a DM can do at a table.

Here is the elephant in the room, however: While characters can pretend to forget information in-game, you can’t actually memory-wipe your players (unless the flashy sticks from Men in Black have already been invented, in which case, sign me up for one). The funny thing is that you don’t even need to. Players usually do it to themselves already.

Every DM knows that players are not always great at keeping track of information or remembering things. It’s understandable since they show up to the table to relax, have fun, and eat unhealthy snacks. You can’t expect them to remember the 50 pages of lore you wrote this week, or sometimes even the name of the person who’s been giving them quests for the last month. Here is where the False Hydra’s powers become even more interesting, especially if you run this monster over multiple sessions (or even an entire campaign). It turns one of the most annoying things for a DM into a boon. If your gaming group doesn’t like taking notes, it’s time to unleash the False Hydra upon them.

Image: Marcelo Orsi Blanco

Of course, it’s impossible for an entire group of players to completely forget about an NPC. But as the DM, you can set up things in a clever way so that your player will at least be confused: Are we not remembering things because we didn’t take notes, or is there some dark power at work? This works best as long as the players have not discovered the truth about the False Hydra and its power — which they shouldn’t until the climax of the adventure. The most chilling moment occurred when my players finally saw the beast and realized that it had been slithering around them all this time, its pitch-black eyes staring at them through a window, its deformed mouths salivating with hunger.

However, even if players are mostly aware of what’s going on, this setup still yields great roleplaying results. In my adventure, there was an entire sequence where the players visited the house of a former party member who had retired and moved to the village now infested by the False Hydra. After the first visit, the NPC was eaten, so I told them they had no memories of this person. During the second visit, they perfectly acted as if they had never been in that place, so much so that I thought they actually forgot the details of the house from the previous session — and in fact, some of them did, until I kept adding more small hints.

It’s a rare case of an in-game feature coming to life at the table, and it’s also why I think the False Hydra is one of the best D&D monsters. You can’t disintegrate your players while they’re fighting a Beholder, but you can play tricks on their memory if they are facing a False Hydra. It takes some setup and careful thought, but the results are absolutely worth it. If you decide to try this awesome monster at your table, here are some tips I learned from my attempt.

Image: Shry99 (Reddit)

First, make the False Hydra the center of the story. I added another plot about the dark past of the city, an innocent witch, and time distortions. It was fun, but impossible to fully unravel in two game sessions. This monster is so good that it deserves all the spotlight. Second, spend some time preparing the False Hydra stat block. It wasn’t included in Arnold Kemp’s original post, and people have made attempts to create one over the years, but I find them all lacking something. Turning the Hydra Song into a game effect is particularly challenging. If you allow a saving throw, and one or more players succeed, this could hinder the adventure from the start. If you don’t allow a saving throw, then you have to think about how the players will discover the truth. I used an NPC that was a child with impaired hearing, who made some creepy drawings of a monster (I figured that partially hearing the song made the False Hydra appear intermittently), which led to the characters sealing their ears with wax.

There is a lot more about the False Hydra than I wrote here. I suggest reading the original post, where you’ll also learn about the terrifying “stage two” of the monster, which makes it the perfect villain for a long campaign. Overall, the only flaw the False Hydra has as a creature is that you can only use it once on your players.

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