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Infinite Regress

by John Atom from Threshold Magazine issue 24

A short adventure for any party


Infinite Regress is a short one-room puzzle/adventure wherein the players must find their way out of an illusion crafted by a powerful wizard. It is entirely system neutral except for a few stat blocks in the end which assume the 5th edition ruleset, and it is compatible with a party of any class composition or level. The adventure takes place inside an inn located in the Grand Duchy of Karameikos (the choice of town or village is left to the DM). It is intended to serve as a minor challenge for the PCs while they rest between adventures.

By some ill luck or circumstance the players are trapped inside a mirrored hallway (in reality an illusion created by the wizard Hipparchus) that is essentially an infinite loop. No matter what direction the PCs walk, they will end in exactly the same hallway. To leave they have to solve an easy and relatively obvious puzzle involving just a tad out-of-the-box thinking.

The adventure will introduce a new NPC (the wizard Hipparchus), a new monster (the Peeping Doppelgänger), and a new spell (Summon Peeping Doppelgänger).


In recent weeks, a wizard by the name of Hipparchus has been spotted traveling around the less populated areas of Karameikos, offering his services in exchange for gold, and most unusually, information about local lore.

A powerful yet clumsy wizard, Hipparchus (aptly nicknamed, Hipparchus the Forgetful, for reasons that will become apparent later on), has left his Alphatian homeland to travel the world and increase his knowledge and understanding of the “magical arts.” While a renowned and feared mage in times past, these days Hipparchus seems concerned with nothing but the scholarly pursuit of magical knowledge. No one knows to what end. Speculations of those who've met him vary wildly, from the exaggerated claims that he's trying to create a new kind of weapon, to hand-wavy resignations that the infamous mage may simply have nothing better to do in his old age. Similarly, no one knows why Hipparchus left Alphatia.

Entering Hipparchus’ Room

This adventure assumes that the PCs will reside in the same inn as Hipparchus, who being used to certain luxuries, will likely have booked the most expensive room available. The DM must supply a motivation for the PCs to enter Hipparchus’ room. This can be accomplished in a number of ways, but the simplest one is to have the innkeeper begrudgingly mention that “that damned wizard forgot to pay his bill again.” The innkeeper may ask the PCs if they could “kindly stop by the wizard’s room and remind him of the bill.”

The DM may also choose to throw this challenge randomly at the players if they decide to go ‘snooping’ around on their own.

The wizard always leaves his door closed, but unlocked. If the players knock on the door before entering (the DM should call out their rudeness if they don’t!), they’ll hear a distant-yet-crisp voice from inside the room mutter, “come in….”

The Infinite Hallway

Once the PCs enter Hipparchus’ room, they’ll find that it is unlike any other room inside the inn. Gone is that warm and hospitable feel of the hardwood floor, and gone are the fragrant smells of fresh stew and bubbling ale. Instead, the PCs find themselves in a narrow hallway (10 ft wide, 50 ft. long) with granite floors and large mirrors covering the entirety of walls on either side of the hallway. If the adventurers look up, they’ll notice a chandelier hanging from the ceiling, approximately 15 ft. up. Finally, there’s a door at the other end of the hallway, identical to the one from which they entered.

Immediately after the PCs walk in, the door behind them will close shut with a thundery echo that reverberates for a few seconds. Inside the hallway, the PCs will notice some or all of the following effects:

Escaping the Infinite Hallway

After their first encounter with the Doppelgängers, the PCs will naturally want to examine this newly created space behind the mirrors, looking for a way out. They’ll find that it is identical to the original hallway, except that there is NO chandelier in this new section of the ceiling. The PCs may continue to break mirrors (fighting more Doppelgängers) enlarging the size of the room, but nevertheless, there is only one chandelier hanging in its original position. This is because the chandelier is part of the inn (i.e. the wizard’s room), rather than the illusion. Hipparchus was too lazy to create a permanent artificial light source for his Infinite Room, so he left the real one in.


Since the chandelier is real, blowing out its candles will plunge both the Infinite Room as well as the real room into darkness. Hipparchus will surely notice the sudden change and wonder what happened. He’ll try to reignite the candles. The players won’t be able to see the wizard, of course – to them, the candles will simply turn on again – however, when Hipparchus is close to the chandelier, the players will hear a faint, distant voice coming from that direction (“since when is there a breeze in here?...”). It will be brief, but the PCs should be able to piece it together. The presence of the chandelier in both environments allows some of the sound to go through. And it works both ways. If the PCs take the opportune moment and shout towards the chandelier (they have to be loud!), the wizard will hear them. Eventually Hipparchus will realize what’s going on and dispel the illusion.

Alternatively, if the players keep blowing the candles off every time Hipparchus turns them back on, the old wizard will eventually (maybe after 5-6 tries) figure out what’s going on and dispel the illusion. He’s forgetful, perhaps a little aloof, but he’s certainly no idiot.


There are a few hints that will point the players towards the solution and inform them about the nature of the illusion (assuming they didn’t pass the initial checks). Should the PCs not get or notice this, the DM should do their best to ‘nudge’ them towards the right direction instead of letting the players wander in the Infinite Hallway.

First, the absence of the chandelier behind the mirrors should be an obvious giveaway, but it is possible the players will not think much of it. The DM may try to bring subtle attention to it. For instance, the PCs may hear (or think they hear) a faint whistle coming from it, if only for a split second (Hipparchus is keen on whistling when stuck on a problem).

At some point the PCs may choose to capture a Doppelgänger alive with the hope of interrogating it. If they do, there’s a 50% chance that the Doppelgänger will simply disintegrate into ashes, and a 50% chance that it will say (in a semi-robotic voice): “Master Hipparchus, experiment 442 observation. Begin recording… Pause recording… Update, experiment on temporary hold due to following reasons: ‘where the hell did I put that tome?’ End recording.”


Out of the Infinite Hallway, the PCs finally get to meet the infamous old wizard. Hipparchus – an olive skinned man with thin white hair tucked underneath his sepia-colored robe – will be standing at the edge of the room, holding a heavy tome by the candlelight. His physical appearance is somewhat disproportionate: the deep wrinkles, sunken eyes, and receding hairline betray the vast passage of time on his face; yet his firm-postured body and muscular forearms posses the vigor of a much, much younger man.

Hipparchus will apologize profusely for the inconvenience he caused. The Infinity Room was part of an experiment he was conducting and eventually lost interest once he realized his initial “hypotheses” were unsound. However, in his enthusiasm to plan the next experiment, he had forgotten to dispel the illusion. Classic Hipparchus!

The PCs will find Hipparchus to be obliging and pleasant-mannered, albeit enshrouded in mystery. He won’t really talk about himself, his travels, or his work – though he has a polite way of turning questions down. As a form of reparations for the ordeal, Hipparchus offers the PCs his magical services (Identifying, Enchanting, Writing Scrolls, etc.), completely free of charge while he’s in town, provided the PCs understand he’s a busy man and won’t abuse that privilege. Note that if the PCs take him to task, there’s a 30% chance he’ll forget about it (though nothing’s stopping them from asking again).

Additionally, Hipparchus will offer the spell Summon Peeping Doppelgänger to the PCs. It’s another one of the wizard’s creations, originally intended as a means of record keeping during experiments (Hipparchus hates taking notes). However the spell has a few ‘glitches’ which Hipparchus does not have the patience to fix. The details of the spell are given in the next section.

Hipparchus plans to stay in the village only for a few more days, before he embarks for the next step in his long journey.


NPC: Hipparchus the Forgetful (HP: 20d6+40)

Human, Wizard (Divination), Lvl 20, Alignment Uknown

Str: 16(+3), Dex: 10(0), Con: 16(+3), Int: 20 (+5), Wis: 13 (+1), Cha 15 (+2)

AC: 20 (Custom Magical Robe)

Speed: 30ft.

Background: Hermit

Proficiency Bonus: +6

Proficient Skills: Arcana +11, Investigation +11, History +11, Nature +11

Saving Throws: Int +11, Wis +7

Darkvision, 60ft (from Enchanted eye-glasses)

Spells (Spell Save DC 19, Spell Attack Mod +11):

NEW SPELL : Summon Peeping Doppelgänger

3rd level Conjuration

Casting Time: 2 minutes

Range: 10 ft.

Components: V, S, M (a bucket of mud or wet clay)

Duration: 1d4 days / caster level

This spell summons a Peeping Doppelgänger. Initially, the Doppelgänger exists in its natural form until commanded by the caster to assume the appearance of another humanoid creature. This command need not be specific – for example, the caster can ask the Doppelgänger to take the form of the first humanoid that enters the room, whoever that may be. However, the humanoid must be one that either the caster or the Doppelgänger has seen.

Upon transformation, the Doppelgänger will permanently assume the appearance, equipment, and stats of the humanoid it is mimicking, but it will not possess the original’s magical abilities. Thus, the doppelgänger is able to mimic all physical attacks and moves, but it cannot cast spells or benefit from any magical bonuses or effects (this includes weapons, most class or racial abilities, etc.). For example, a longsword + 1 will simply be a longsword in the hands of the Doppelgänger.

The Peeping Doppelgänger may be used only for the purpose of surveillance or observation, as it has an uncanny ability to blend in with the environment. Immediately after the creature is summoned, the caster must give it detailed instructions regarding its mission and hiding place. The hiding place can be something as simple as crouching behind a closet, or as elaborate as the example used in this adventure – but in either case, it must be tied to a single location. In this case, the DM and players must come to a mutual agreement about what constitutes a “reasonable” hiding place for the Doppelgänger.

The Doppelgänger will remain in its hiding place and record everything it sees or hears for 1d4 days per caster level, or until dispelled. At any point during its lifespan, the caster may visit the Doppelgänger and receive a detailed report of everything that has happened. If the Doppelgänger is discovered by anyone other than the caster, roll a d20 for the following effects: