The Tarterian Highway (Part 2 of the “Low-Prep, Reusable Scenarios” Series)

A Tarterian Highway. Image by Graham Robert Scott.
A Tarterian Highway. Image by Graham Robert Scott.

The Tarterian Highway

The Scenario in a Nutshell:  A fun twist on the random Nostalgia Crawl is a Vault of the Drow-style dungeon, or what I’m calling the “Tarterian Highway.” It’s a linear dungeon crawl toward a specific objective, with most of the foes having some sort of culture in common. You’re traveling through enemy territory on a mostly straight-line trek from bad toward worse.

Making It Work: First, stick the party in an enclosed setting: a cave system, the Underdark, another plane of earth and tunnel, the Demonweb Pits, or whatever.

Second, make this setting part of an empire of nasties: dark elves, Lovecraftian fish people, wights, stone orcs, troglodytes, or whatever else you wish so long as it’s level appropriate for the party.

Third, make a quick list of available stat blocks and Challenge Ratings for the race that owns the empire and for other pets, beasts, minions, allies, or pests they might have. The Vault of the Drow (a classic old-school dungeon from 1978, see here or here) has pretty good examples of simple encounter tables based on such tight lists. If you’re building your own, you could instead fill in the basic template below:

 2d6 result  Type of Encounter
2 A lone but formidable member of the local civilization
3 An adventuring party or elite team from the local civilization
4 A large patrol from the local civilization
5 A small patrol from the local civilization
6 Several members of the local community walking
7 Farmers or shepherds tending to some kind of local food source (likely exotic)
8 A few travelers who do not belong to the dominant culture (possibly keeping a low profile)
9 A creature or beast allied with the dominant culture
10 A wild beast or creature with no allegiance to anyone
11 Escaped slaves or prisoners
12 A potential ally with considerable political, physical, or magical power

Once you have a map and an idea of the race that dominates that landscape, give the party a simple mission that requires them to head deeper into that enemy territory (rescue a hostage, retrieve or destroy an artifact, etc.).

Now for the “highway” part. Tell the party that it’s in a large passage – large enough to fit dragons – heading only two directions: forward or back. If it helps, imagine or use photos of a supercave. Or watch the National Geographic video below. Assuming the link still works when you click it, from 2:02 minutes to 2:49 minutes, it provides a virtual tour of Vietnam’s staggering Hang Son Doong Cave system.

Your adventurers should see frequent signs that this enclosed highway is regularly trafficked, and earlier signs the party has collected indicate that at the far end of this highway is their destination. All along its route, smaller passages branch off (see my own map above for an example), open for exploration and providing ways for creatures to enter the scene.

You don’t need to map these side routes.

Instead, if the party starts exploring them, roll 1d6 on a simple random generator like the one below, which is set up to return them eventually to the main cave. Each time a path forks, use the same table to resolve where each fork leads, as it is explored.

Modified Die Roll Description of Result
1 or lower The PCs’ current passage winds and returns to the main highway.
2 The current passage dead-ends.
3 The current passage turns or bends if necessary to become parallel with the main highway. This lasts for 120 feet. Reroll to find out what it does at that point.
4 The current passage opens up into a larger chamber of 1d6 x 10 feet by 1d6 x 10 feet. This chamber has 1d3 exits. Whenever this result is rolled, subtract 1 from all future rolls for this particular tunnel subsystem. This modifier is cumulative with all other modifiers generated on this table.
5 The current passage turns or bends if necesary to lead away from the main highway. Whenever this result is rolled, subtract 1 from all future rolls for this particular tunnel subsystem. This modifier is cumulative with all other modifiers generated on this table.
6 The current passage branches into 1d3 random directions. Whenever this result is rolled, subtract 1 from all future rolls for this particular tunnel subsystem. This modifier is cumulative with all other modifiers generated on this table.

If you use the above table (or one like it) to handle diversions, the party will invariably end up back at the main highway because the negative modifiers from results 4-6 add up quickly. At some point, they end up with a “1” and come full circle. However, the process will contribute to the sense of a massive, unknowable cave complex without forcing you to prep miles of maps. Moreover, at some point the party will start to ignore the side-treks and stay on the main highway.

For each diversion down a side passage, check for a wandering monster using one of the terrain-oriented monster encounter tables in the Dungeon Master’s Guide or in a similar list of likely critters or patrols that you’ve built yourself. If a monster is indicated, assume it lairs in that smaller tunnel system.

Along the main path, in addition to checking for the odd patrol or wandering creature, also assume that every 1d4 miles, the party encounters a structure of some sort. To determine the type of structure, roll 1d6 and/or make a judgment call:

  1. Perimeter wall or barricade. The wall blocks further progress down the cavern and may go all the way up to the ceiling. Such a wall often marks the start of a territory within the dominant civilization, or a layer of its defense system.
  2. Garrison or abbey. A well-guarded and fortified dormitory, the site might be abandoned or it might be well-populated. Usually it will be located in a side cavern or complex of tunnels off of the main highway.
  3. Tower or keep. A fortified structure with good lines of sight and located at some key terrain point, such as an underground river or tunnel junction. The tower or keep may go floor to ceiling. Towers might be carved into stalagmites or large natural columns.
  4. Fortress, academy, or temple. The structure is as populated as a garrison, as fortified as a keep, and as civically focused as an abbey, with either a martial, arcane, or divine training mission, on top of any other missions. Like the wall, this structure might very well block through traffic on the highway.
  5. Home or tomb. Tucked into a wall, smaller cave, alcove, or pit is the guarded resting place of something either living or dead. It might be dangerous either way.
  6. Ruin or underground city. The already-massive cavern expands. The vaulting ceiling grows more distant; the floor slopes down. And within this bubble in the Earth (or wherever), someone has created a massive settlement. Likely walled, the city might be full of xenophobic local rulers and their troops, or it might be a silent necropolis, or it might be abandoned for reasons mysterious and disturbing.

For each of the options indicated above, draw on an appropriate random generator from the DMG (or an online resource from the links provided earlier in this article) to determine the nature of rooms and their contents. Need a random city generator? Try this one.

Variations on the Theme: The Tarterian Highway doesn’t have to be underground and the party doesn’t have to be on foot. You can take the linear tunnel concept and convert it to just about anything.

  • Maybe the players are climbing an unfathomably large, plane-spanning tree, like Yggdrasil, with the main trunk serving as the highway and the branches acting as those side passages. Maybe the local culture is avian or insectoid, living in fortifications among the branches.
  • Or you could put them on boats searching for the source of a mighty river running along the floor of a deep canyon. (Imagine Riverworld.)
  • Maybe the highway is a magical path through the chaos of another plane — with no walls at all, but certain danger for anyone stepping off of that path. (Imagine Queen of the Demonweb Pits.)
  • The party might be on a ship on the ocean of an obscure demiplane, sailing in arcane and hazardous seas: If they venture from the current they are on, they may be lost forever, but by staying on the trade currents, they risk encounters with the ships of the dominant local power.
  • Or perhaps the ship is a Spelljammer ship and they’re in fantasy space, but still confined to a linear corridor with dire consequences should they stray.

Quick Links to Other Parts of this Series

1. The Nostalgia Crawl
2. The Tarterian Highway
3. The Sandbox Campaign
4. Glen Cook’s Goblin Recon
5. The Arena
6. Blending Scenarios & Reading Recommendations

♦ Graham Robert Scott writes regularly for Ludus Ludorum when not teaching or writing scholarly stuff. Like the Ludus on Facebook to get a heads-up when we publish new content. 

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