Eureeka’s Castle D&D 5E: The Castle

WARNING: Mature Content

I obviously love Eureeka’s Castle. Let’s be plain about that. I really do—it was a formative thing of my youth, I still remember the theme song, and I think it is a wonderful children’s television program. If you have children, or if you are yourself a child, consider queuing up an episode or two instead of reading what’s below. If you are like me however (a jaded adult with a treasure chest of complexes) then by all means continue onward.


The wind-up castle music box in which Eureeka and her friends lived was for many years an idyllic place, protected from the outside world by the giant that called it his own. This period of peace and grace came to an end when their lives irrevocably changed with the death of their master—felled by a group of nefarious adventurers. As the villainous explorers divided up the spoils from the murder it was Carstigle Wormhand, a mage that long ago delved into the forbidden arts in blood-drenched studies that twisted him to utter evil, that immediately declared that all he desired was the innocuous toy.  

Carstigle took Eureeka on as his apprentice—though not without resistance. Sensing the corruption pervading his magic she refused his tutelage for years, and it was only as her friend Mr. Knack lay flayed open upon the stone courtyard of her home and on the brink of death that she finally, reluctantly agreed. At first she was driven to learn and master his foul magical disciplines so that she could turn against this new master, but the more she delved into the forbidden arts of blood magic the greater her desire was to reveal all that it could offer her. 

Eureeka never forgot the promise she made as she agreed to become Carstigle’s apprentice however, and after a decade of learning all he could teach her the student became the master. Despite how twisted her own heart had become, she learned well how to conceal her true feelings and never allowed her pleasant demeanor to diminish, lulling the aging mage into the fatal mistake of trusting her. As the old man slept in his bed she crept up onto his pillow, snipping off but a strand of his few remaining hairs. Retreating back to the courtyard of their castle she called out all her friends and as the sun rose that day Cartigle’s body jerked up of its own accord, walking in unsteady steps towards his hearth obviously fighting the urges controlling him with every inch. It did not do him any good. Firmly in Eureeka’s mystical grip, he drew out a poker from within the embers of the fireplace’s dying flames and plunged it into his own gut—at first, followed a few moments later by a violent jerk to rip it back out so he could pluck out each of his eyes before shoving the scorching iron down his own throat. 

There was no celebration upon their tormentor’s death, no consolation or resolution or relief. Only the realization that his horrors had come to an end. With their newfound freedom there was a brief period of a few months where the denizens of the castle attempted to return to their former lives, but too much had changed, too many had suffered too greatly. Once again it was Eureeka that brought about change. After she had finished exhausting the books and tomes within her dead master’s library she found that the greatest obstacle to her attaining more power was a simple one: blood. She needed blood. With hearts that grew colder by the day, she convinced and cajoled nearly all of her companions in helping her gather victims to sacrifice, ensuring them that even one child would provide more than what her studies could possibly require. After the first of these was lured away to a gruesome, excruciating death they found it less difficult to kidnap the second, the third, the tenth, the twentieth. Carstigle’s keep has since become an abattoir of slain youths and many in the region whisper that they have heard the cries of children from within, though none of the few courageous souls that have gone to investigate have yet returned to confirm the rumors…


Shrinking Magic. All of the creatures within the music box are actually Tiny (or if listed as smaller than Small-sized below, too insignificant to have statistics in the regular world), but the powerful enchantments imbued throughout shrink down interlopers to the same scale as the extremely short local population. If for some reasons they are taken directly out of the music box, Magellan is 1 foot tall, and most of the rest are only 5 or 6 inches in height.
Any non-giant creature that inspects the music box, touches it, or hears its music must make a DC 30 Charisma saving throw. On a failure, the creature is shrunk down to Tiny size (only a few inches tall) and lands in the courtyard of Eureeka’s Castle. The creature remains this size until it finishes an uninterrupted long rest, at which point it is teleported to the nearest unoccupied 5-foot square and awakens. Only a dispel magic cast using a 9th level spell slot or a wish spell can cause a creature shrunk by this magic to return to its normal size.
These magics wreck havoc with planar physics. While within Eureeka’s Castle all spells and magic items that create or use extradimensional spaces cease functioning. In addition, attempts to teleport beyond the range of the realm’s shrinking magic automatically fail.



By spending a vilis point as a reaction, an evil adventurer (or in this case, an NPC with a Sanctity score and Sin score) can do any of the following:

  • Change the damage of a spell or weapon attack to necrotic.
  • Reroll a failed ability check or saving throw. 
  • Gain a +1d6 bonus to an ability check or attack roll so long as it is part of committing an evil act (desecrating a holy object or place, delivering a poison, preparing a murderous ambush, telling a hurtful lie, and so on). At 10th level (or CR 10) this bonus increases to +2d6.
  • Delay the effects of a spell for 1d4 minutes per spell level. By casting a spell at a spell slot one level higher, the delay can be additionally increased or decreased by 1d4 hours per spell slot level (with no other benefits of casting the spell at a higher spell slot).

More information and details on Vilis Points can be found in the free Book of Exalted Darkness: Evil Primer.


Modified from

eureeka's castle dnd 5e castle map draft uno 7.2

1: Courtyard
The Fishtones dwell beside one of the fountains on either side of the entrance to the castle, switching which usually at least once a day. They are keen for any kind of entertainment and attempt to lure people that wander nearby the music box to evaluate it or listen to their performance, allowing the magic to bring them a new trespasser.

2: Dining Room
The table in this area has been put to horrendous use so Eureeka had Magellan smash it, spurring the dragon on as he tore through everything within. No one has made any attempt to clean it, and instead the castle mice have taken up residence in the chamber’s detritus. 

3: Kitchen
This is the only room that Magellan routinely visits inside the castle proper these days. Unfortunately he has not had peanut butter and jelly sandwiches for years, instead consuming ground bones and blood flavored with illusions courtesy of Eureeka. The Moat Twins have managed to steal one or two but have seen through the magic and don’t bother to try and take any more than that—and they are now more scared of running afoul of the dragon that so cherishes the sandwiches.

4: Study
This area contains all the crafting materials and toys that the castle’s denizens used frequently before the time of Carstigle. It has largely fallen into disuse but a DC 14 Intelligence (Investigation) check made while searching through it reveals a stash of expensive material components worth 1,200 gold (the specifics are at the GM’s discretion). Sir Klank can usually be found here.

5: Throne Room
Murals, tapestries, and sculptures line the walls of this chamber, each depicting both tragedy and triumph. When he deigned to come to the castle, the wizard Carstigle spent most of his time in this room. It is still scarred with the many depredations he inflicted on the people here, though Mr. Knack has taken to memorializing how they overcame those sufferings, hoping that beautiful artworks will touch upon some of the good within Eureeka’s corrupt soul and catch it alight. 

6: Belfry
Batly and Webster still live in the belfry at the top of the castle, though their balcony has fallen away and to keep out some of the horrors that sometimes crawl throughout he has bricked up all the doors (and most of the windows, though not entirely). Whenever there is any commotion from the Courtyard the werebat investigates, assessing whether or not newcomers can be trusted or if they too pose a threat.

7: Storage
A number of cages are situated throughout this room, some of them occupied by kidnapped children. Eureeka has never been specific about the types of people she needs for her further research into blood magic—only that they be young. It doesn’t take long for even the slowest-witted child to figure out their fate once they arrive in this chamber however, and they beg anyone they see to free them and help them escape this horrible place.

8: Knack’s Room
Mr. Knack keeps his bedroom and work area fastidiously clean and it is the only sanitary area within all of the castle. Anyone that searches this chamber with a DC 24 Intelligence (Investigation) check reveals a perfectly seem-fitted floor panel concealing what must be years of research into magical redemption, legends of people that have returned from paths of evil, and the like—and at the very bottom, a scroll of wish written in Infernal with blood instead of ink.

9: Moat Twins
This room has direct access to a waterway that feeds into the moat surrounding the castle. Bogge and Quagmire spend the vast majority of their days here playing juvenile games where they swim down into the muck to pull up foul relics they’ve buried there before, but if they aren’t lounging on the stones or the water the Moat Twins are out somewhere causing mischief (likely stealing something).

10: Eureeka’s Chamber
Keen to keep her powerful guardian close and loyal, Eureeka moved into the chamber beside the dragon’s lair before murdering Carstigle and she’s had no reason to leave since then. It’s more convenient anyway—she spends all of her time down in this area, only occasionally going up to acquire a new subject from the storage area when the current victim has expired.

11: Magellan’s Lair
This is where Magellan lives, though his bed has been in tatters for some time now and one would only ever know it is his by the presence of his pets (Cooey and the Slurms). Anyone with a passive Perception of 17 or higher notices that near where the dragon sleeps there are very crudely etched symbols that vaguely resemble holy shapes (left there by Magellan’s tail while he sleeps).

12: Ritual Chamber
The walls and floor of this rock-hewn chamber are drenched in blood and it reeks of evil. When a creature of good alignment first enters into the area must make a DC 25 Wisdom saving throw or gain the poisoned condition for 1 minute. At the end of each of its turns, a poisoned creature can repeat the saving throw, ending the effect on itself on a success. Once a creature has been poisoned by this effect or successfully resisted it, it is immune to the effect for the next 24 hours. There is a 50% chance at any time that a nearly dead child is being flayed alive within, though saving their life will require powerful healing magic (like heal or regeneration) and they will certainly be traumatized even if they survive.

13: Hidden Study
A passive Perception of 15 or higher is required to notice the presence of a secret door here. There is no mechanical way to open it however, and looking at it with detect magic only reveals that it has some kind of divination enchantment. When a creature uses a bonus action or action to spread blood on the wall (at least 1d4 hit points worth) the doorway slides away into the floor to reveal an extensive library. The shelves are lined with rare tomes almost all of which are on subjects of necromancy, blood magic, torture, and other often forbidden topics that many would call evil. At the GM’s discretion, there may also be magic items hidden in this area (though preferably most of them are cursed), but even if not at least 1d4+1 of the books within are magical.


  1. This is just so fabulously wonderful! Thanks for sharing all this beautiful wildness; it’s such an unusual idea and it works so well! Seems like it’d be a really fun play. Eureeka’s Castle is great ❤

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