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Vast Underground

Megadungeons in Fantasy HERO by Jeffery Keown

“Deep Aura don't fit on no treasure map, son… it goes on for the rest of your life.” –Overheard at Delver's, Chalkcliff Merchant Quarter

In Caleon, we have a few dungeons that rival cities in their vast scope. For miles their tunnels and passageways stretch, vast open spaces acheived by precious few tunnels only a meter or two wide. Their names send chills down the spines of the most seasoned delver; Deep Aura, Twilight Caverns, Besmirk, Ancient Regio, Yathlaan and probably a dozen others. The older your world, the more of these you are likely to have.

There are resources Down There. The nations of the world know this and have, from time to time, sent bands of talented individuals into these nightmare realms only to find they are beyond the ability of small parties. Entire legions have gone into these places, only to have scattered, maddened survivors limp home with a pittance of loot.

Why do the guilds and governments raise troops to throw at these Megadungeons? The reasons are as numberless as the powerful people who commission these doomed delves. Guildmasters, Kings, Merchant Princes and military men are all fond of sending hundreds to their deaths to secure a large diamond, enchanted scepter or a scrap of parchment that might lead to yet another sunken, accursed city.

Even worse is the notion of Gamemastering one in your own campaign. In a white hot burst of inspiration, I will herein try to capture the logistical nightmare of a Megadungeon. Such heat often leaves in its wake deep scars and certainly dire burns. Corrections, clarifications and after-market assistance are, as always, quite welcome.


Why do this? Why go to the headache of designing a Megadungeon if you're only going there once? Simple… that one trip will take months to game through! This will keep parties busy for weeks on end, provide ample loot, throw political intrigue, stealth, magic and all-out brawls into every episode you run for a good long time.

Some Terms

Faction - One “side” or force of creatures struggling for control of a megadungeon.

Hall - An area of relatively easy access, somewhat cutoff from it's surroundings. An example, using the idea of a vast underground city would be a residential area. One or two ways in, but each area inside is very open and accessed quickly.

Loot - Anything of value; magic swords, treasure, slaves, art objects, armor and weapons.

Natives - The lifeforms (or automata) present in the megadungeon when the struggle begins.

Trap - A mechanical deterrent. Often of a one-shot nature. Sophisicated ancient cultures might have created auto-reloading magical traps, however, but those might be called wonders.

Wonder - Non-mechanincal traps assets and features, usually recharged by ambient magic, Magic Healing/Buffing pools, Teleport chambers, Illusory rooms and objects. Room of Regeneration anyone? These will always be coveted by one or another faction.

Design Considerations

Location Where is the megadungeon situated? How was it constructed? Is it square miles of twisting natural caverns and water-carved tunnels? Or is it some ancient Dwarven city, built by stubby hands over thousands of years? While the concept begs for a location removed from polite society, the image of a teeming labrynth below the campaign city's streets is appealing.

Entrances How do you get all those troops down there? Perhaps a vast bridge over a waterfall leads to a great set of doors that have recently been opened. Or the entrance is more mundane, a simple rune-carved hole leads to glory and doom. Each entrance is likely to be controlled by a faction, or is the focus for an active contest for control. If there is only one entrance, it can be the scene of constant fighting

Factions Present How many factions are struggling for this bit of real estate? Even if you do not include guilds, cults, more litigimate religious organizations or governments, there's still the current tenants versus the Player Characters. That's two right there!

Faction Territories Depending on the layout, number of entrances and so on, factions may have secured certain areas for themselves. This, as in the case of Entrances, is one of determining preparedness. Factions will want to secure areas that are easy to defend, or contain the loot they wish to claim. It helps their cause immeasurably if these features are found in the same Hall. Most of the time, anything worth taking home will be very hard to get to, so this might not seem so unreasonable.

I like to keep things simple, and break things down by security level (see Encounters, below). At a glance, the SL of a hall determines a great many things.

Faction Size How many in each faction? This ranges from around a thousand low-point troops and support personel to six people roughly equivalent to the Player Characters in point cost.

In fact, start with those six. One of them is the leader, his point cost is 110% to 150% that of the Player Characters. He's got five buddies almost as dangerous as him. They have points roughly equal to the Players. Or, more fitting, they are just as capable, but perhaps built with more “Economy of Design” that allows you to concentrate on their combat-oriented abilities, rather than producing a detailed character sheet for each one. They are teh group with the most complicated motivations. Everyone beneath them in power is probably just here to do their job and hopefully get out alive.

Below those folks are Scouts, Elite Troops, Guards, Loremasters and bookkeepers, cooks, and skilled and unskilled laborers. As the points go down, the population increases. Not that you'd have hundreds of 25-point cooks, but you might, it depends on how much a given faction likes its food.

That brings us to how many of each type a given faction brings along. One designed to get in and out fast won't bring a cook, but if they plan to colonize the place, expect to see everyone you might normally find in a city environment.

Size of faction is also determined by how long the faction has been involved in the conflict. After a few weeks, one would expect reserve forces, smiths and a supply train.


Encounters are based on the Hall in question. If it is newly entered by a rival faction, there may be “natives” to deal with in addition to the rivals.

Random Encounters usually take the form of a chart, keyed to each hall. The chart will consist of encounters with every faction who claims the area, plus any remaining traps, wonders or native life.

Programmed Encounters should be more than just bumping into the enemy faction around a corner (though it might be just that). They should be scenes that PCs interrupt, view from a safe distance or hear from afar. An example would be a research team in the process of opening a vault. The Player Characters hear the Spells of Opening, listen for a while to the conversation of the rival team and rush into replace them at swordpoint. The treasure in that encounter is relatively light, consisting of the rival's gear and tools, and a puzzle to work out (the vault).

Some GMs prefer to never use Random encounters, instead coming up with programmed ones on the fly, or in a burst of activity, write an entire Hall's encounters before the game, which allows a good deal of realism that off-the-cuff encounters can lack. Programmed encounters can also be a drawback, what with no scene ever going off as planned due to player action, which is highly unpredictable.

Security Level

Security Level tells you what sort of encounters, loot and native life you might have to deal with. Think of security level as a palette of colors you will paint the area with.

Unexplored - Newly discovered by one or more factions, the area is ripe for picking! Native life will be at its peak, treasures will be undisturbed (unless the natives are intelligent folks like Orcs or Drakine or what-have-you). In that case, the area is most likely Secured by the native faction. Any rivals will be scouts. Eliminate these, and you set into motion a whole slew of encounters with natives who heard the fighting, reserve forces investigating the scout's absence and finally, the high-end party who shows up to really clean house.

Claimed - One or more Factions claims this area. Any fighting is sporadic, no units will have been committed to the area as yet. Only scouts and maybe a guard force will be present. Even then, they will only be encountered near their faction's entrance to the zone. Native life is present and possibly aware of the actions being taken to destroy them.

Contested - Regular clashes between rival factions is the order of things in a Contested Area. Expect to see all native life driven out or killed by the fighting, probably a quarter of the loot is missing, but then, a similar percentage of traps and wonders will have been set off and not re-loaded.

Hotly Contested - Constant Dungeon Wars action! Night and day, troops are being sent into prevent the loss of the Hall to a rival faction. Any loot discovered is either being used in the fight, or awaiting other Faction members to haul it off.

Secured - One faction has won out over the other(s). The area is relatively secure, troops and support are able to actually sleep in some state of comfort and peave of mind. Research teams are scouring the place for un-tripped traps, loot and resources Encounters in such an area include well-fed and well-rested troops who know the terrain like the back of their hands. Any loot uncovered in this area has been moved to the Faction's base camp (either outside, or in another secured Hall), or is awaiting shipment. Conveniently, Player Characters who win through this kind of area have their loot boxed, labelled and ready to steal.

Abandoned - This area has been well and truly picked clean, perhaps it contained nothing of value, or such resources were not discovered. Encounters in an abandoned hall almost certainly include critters driven from their homes in other halls. This motivates them to extra voilence against the first thing they encounter.

Creating Halls and Areas

Name it. Even if the Player Characters never hear the name, the inhabitants certainly call it something, and the rival faction's troops have names for the areas for quick reference. While you can call the Hall just before the Big Open Space Area A, its much more fun and flavorful to overhear an enemy sergeant refer to troops moving into Vile Demense north of The Canyon. Names should be based on the type of native life encountered there, as well as archectural features such as wells (“Well of Life”), narrow passages (“Noosfal's Squeeze”), high-sided open areas (“Ambush Alley”) or just really cool design (“Awesome Arches”). Sometimes a bit of statuary or a fresco can give rise to a name. Alternately, what the Faction's commanders call Area 521 North, the troops refer to as Lemmy's Deathtrap in honor of a fallen comrade.

Define it Pick features that will define the Hall to the players. Was this area an industrial sector, filled with rusting armories, cold forges and memories of ringing hammers and long-silent work-chants? Or was it a magical college, filled with traps that summon demons, crumbling libraries and hidden tomes of knowledge. The better you define an area, the more the unusual will stand out when encountered. A perfectly preserved book among piles of rotting tomes will be a signal to all but the most daft of parties.

Populate it. Each Hall will have creatures, traps, wonders and loot. If the above example of an armory is used, consider having armored undead, fire elementals and secret caches of enchanted metal waiting to be discovered. The magical library example might be populated by the spirits of dead wizards, lore-elementals and new powerful magic spells to fight and be fought over.

Game it! Once the population is fixed in your mind, ideas for “side quests” and scenarios might fill your head. This is good. Using the two examples, suppose the armory contains the ghost of a long-dead smith, and she cannot rest until she knows the fate of her love, a wizard of no small talent, now a dread lich who controls the library. Perhaps he can be calmed by the sight of her spirit, or she can laid to final peace by knowing her love's condition. Sounds like you need to get these two crazy kids together, but between those two halls lay several secured zones, the bastion of an undead hunter and his powerful entourage.

Cinematic Effects

Lava - Extremely silly to have molten rock running like a babbling brook through your megadungeon, but it makes for neat lighting, hazardous travel and provides a hook or theme to the monsters encountered there.

Water - Not quite as dangerous as magma perhaps, but certainly good for forcing swimming, air supply issues and providing secret passages that aren't immediately obvious. Sure there's a pool in the room the PCs are sleeping in, but that's just good drinking water. When the evil guys show up, dripping wet, to kill them they'll know they should have been a few points more observant.

Heights The ruddy light provided by all that magma can give hints as to the height the PCs are above the floor, narrow bridges spanning deep cracks provide a certain dramatic flair and fighting on precarious ledges a thousand feet from the unseen cave floor can make any fight more interesting.

Vermin - Albino cave creatures, swarms of rats or beetles, bats by the thousands..not to mention the dreaded fairy swarms found in some particularly awful megadungeons.


The Big Boss In Deep Aura, the whole place is ruled over by a being called the Deific. He doesn't mind the player characters coming in, he doesn't mind them killing a few dozen Ur-Grubs. He does take them to task for shutting off the Fire Fountain and stealing the Eye of Chaos. In the case of Deep Aura, there is a limit to the active points he'll allow to be cast in his domain, as well as a list of specific actions he won't tolerate.

Consider having a powerful creature, demon or undead automaton as a Hidden Faction. Hints of this character abound, but he does not reveal himself and his forces until some specific action is taken.

Multi-layered battles Similar to seiging a castle, a multi-layered encounter can be great fun. If the party is pleased with uncovering the Tomb of Laarn, perhaps they'd enjoy fighting for it not with folks rushing down a narrow hallway at them, but a large force of archers in balconies four stories up? They will be pleased with both finding the tomb and the victory over the rival force. Give them 5 archers and six guys rappelling down the walls, plus a wizard throwing fireballs from one high and they'll never forget the battle. They also won't forget to look up on occasion.

 Vast Underground ()