The Inverted Jungle as 3-D Hex Crawl

[Note: there is a more recent version of these rules, available here.]

The White Jungle is an immense riot of fungal blooms that springs downward from the bottom of Zyan. At the highest level, the huge trunks of white "trees" spring from massive interconnected root balls that cling the island above. In the blackness of the highest level they branch out, flowing together into a lattice of interconnected brambly thickets, punctuated by sudden drops into the darkness below. In the next level a dim light penetrates upwards from below. Here the jungle is densest, sprouting into a series of stable interconnected branches, bearing white trembling fronds, and milky vines. One level further down, the jungle becomes bright and airy, but here the growth thins, and movement becomes more perilous. In the lowest level, some islands of growth descend even lower into the endless azure sea. Here, even the most careful travelers risk plummeting into the heavens below.

The white jungle is a 3-D hexcrawl with the constant possibility of falling. What follows is the current set of rules I am using for running. I have playtested once so far, and they seem to work well. My goal was to keep it somewhat abstract, so that we didn't get bogged down into details about how people were tying off to one another, and what the method of movement the party employs across different micro terrains. (Such quotidian details are not appropriate for the exploration of an inverted jungle in the dreamlands!)

I want the system to be one where the players know the risks and rewards, where this induces some choices about resource management, and where the rules are potentially deadly, but not too complicated. What I came up with is somewhat fiddly, although not much more fiddly than encumbrance rules. If you're going to be running a hexcrawl in an inverted jungle, it seems worth having some subsystems to dramatize the risks and tradeoffs players face, even at the expense of a little crunch.

Movement 

PCs can move in three dimensions in the White Jungle. They may travel up, down, or any of the eight normal hex directions. Moving any normal direction costs 1 hex of movement. Moving up a hex costs 2 hexes of movement. Moving down a hex costs 1 point of movement. There are also some areas where travel in some directions is hampered by natural obstacles. In this case, it takes 2 hexes of movement to travel in the hampered direction. (Hexes are 1/2 mile wide, and I'm using stacked hexmaps each representing a jungle level.)

There are three levels of security that PCs can employ that affect their movement rate: unsecured, lightly secured, and heavily secured. 

Unsecured: When unsecured, the PCs are traveling without some system of ropes. They can travel more quickly this way, moving 5 hexes worth of movement a day. However, this is dangerous, so they must each make a falling check for each hex they move through as per the rules below. 

Lightly Secured: PCs are traveling with some system of ropes, but are keeping it loose. They may travel 3 hexes a day. They do not have to make a falling check when moving through a hex and receive a +1 to their checks for falling when a situation that warrants a check does arise.

Heavily Secured: PCs are traveling with a system of ropes, and are playing it safe. They may travel 2 hexes a day. They do not have to make a falling check when moving through a hex, and receive a +2 to their checks for falling when a situation that warrants a check does arise. 

The party may opt to move an additional hex above their allotted movement without resting for the night. The first hex requires everyone to roll 4d6 under Con. Those failing take -1 on all rolls, including falling checks, until they sleep. The second hex pushed, and every hex thereafter, requires 5d6 under con. A second failure means the person suffers -2 on all rolls. If a person fails three times, she cannot go further and simply must rest.

Sleeping in the White Jungle is awkward. Without either finding an unusually secure spot, or having proper gear, one must sleep precariously and uncomfortably perched among the branches of trees. Those sleeping under those circumstances must make a 3d6 under CON check to get a good night's rest. Failure means taking a -1 on checks, including fall checks, the next day. Spellcasters who fail cannot memorize new spells.

Getting Lost

This is a dense alien jungle. When moving through unexplored hexes without landmarks to navigate by, there is a 1 in 4 chance per day that the party will become lost. (If the party contains a ranger, the chance drops to 1 in 10.) The DM will dice randomly to see in what hex they became lost om and move them from that point on in a random direction. On the following day a new check is made. Provided the party does not fail, they will then realize that they are lost, although will not know in what direction they have moved or how far. (They may then try to backtrack.) If they stumble upon an explored hex, they will also realize their error as well as their current location.

Encounter Checks and Combat

There is a 1 in 6 encounter check for each hex the party moves through. There is also a 1 in 6 chance of a nighttime encounter when the party rests in a hex. Unless either party is surprised, something encountered will start 2d6x10 feet from the party. I will roll a 1d6 for elevation: 1-2 it is on a lower elevation, 3-4 the same elevation, 5-6 higher elevation. 

Marching Order and Moving in Combat: Given the treacherous terrain, you can move 1/6 your normal move and also attack during a combat round. A full move is at 1/3 movement rate. The party will declare its marching order at the start of the day; it may be up to two abreast. If the party is not surprised, it can confront opponents in its marching order. If back ranks wish to flank an opponent that the front ranks is engaged with they may do so by going off rope. Flanking characters receive a +1 to hit. [If there are more than 3 enemies, the enemies may flank as well, moving alongside to attack back ranks.] Thieves must also go off rope and furthermore spend a round getting into a good position if they wish to use stealth to backstab. A successful MS check allows them to seize on an opponent's vulnerability and backstab. Failure means they can still attack as normal, with the flanking bonus in the next round. Thieves may only backstab once per combat.

Higher Ground: An attacker with the higher ground receives +1 to hit. 

Damage and Falling: Any time anyone (PC or monster) takes damage in melee combat, he must immediate make a falling check. (Some specially designed missile weapons also induce falling checks.)

Falling Checks

A falling check is incurred if something happens that would be likely to make someone fall, for example, being pounced on by a tiger, or buffeted by sudden winds, or hit by a fireball. TAKING DAMAGE IN MELEE ALWAYS INCURS A FALLING CHECK. Falling checks are also incurred for each hex players travel unsecured. Falling checks are made with climb skill rolls rolled on 1d6. Regular PCs have a base skill of 1. Thieves may have considerably higher base. If a PC's total modified climb skill is 6 or higher, than he moves up the dice chain. A climb skill of 6 rolls a d8 and fails on an 8. A skill of 7 rolls a d10 and fails on a 10. And so on. (Note: these rules employ LOTFP style Thief skills and encumbrance system.)

Climb Skill Modifiers

Unencumbered                        +1

Lightly Encumbered                +0

Heavily Encumbered               -1

Seriously Encumbered            -2

Unsecured                                +0

Lightly Secured                       +1

Heavily Secured                      +2

High Dex (15+)                       +1

Low Dex (6-)                           -1

Jungle Level 1                         +1

Jungle Level 2                         +2

Jungle Level 3                         +0

Jungle Level 4                         -1           

Results of Falling Checks

There are 2 possible results of a climb check: success and falling.

Success: If someone rolls equal to or below her modified climb skill, then they simply succeed in staying right where they are.

Falling: If someone fail a climb check, then they will begin falling.  Someone falling will fall the entire distance they fall in one round. She must make a series of checks. For the first check she fails, she will fall 50’ and must make a saving throw vs. paralysis to avoid taking 1d6. She then gets a second climb check to stop their fall without any previously possessed bonuses for being lightly or heavily secured, since these are now irrelevant. If she fails this, she falls 100’ further and must save vs. paralysis or take 2d6 damage. For the third failure and every failure thereafter, she will fall 150’ and save vs. paralysis or take 3d6 damage. Note that a character may, under unusual circumstances, fall into a lower hex. In summary:

Summary of Falling Rules

First falling check failed

Fall 50’, Save vs. Paralysis or take 1d6 damage, and make a second falling check with no modified for being secured.

Second falling check failed       

Fall 100’ and save vs. paralysis or take 2d6 damage, and make a third falling check with no modified for being secured.

All further checks failed            

Fall 150’ and save vs. paralysis or take 3d6 damage, and make an additional falling check with no modified for being secured. 

Example

Celwin the Conquerer (F2) is traveling in Level 1 of the white jungle. His strength is 16 and his Dex is 10. He is wearing chain armor, and carries 6 items. Normally this would make him lightly encumbered, but given his strength bonus he just squeaks by with being unencumbered. He is playing it safe and so is heavily secured with ropes. Given that he is a fighter, his base climb skill is 1. His total modifiers are: Normal Dex +0, Level 1 +1, unencumbered +1, heavily secured +2. So to make a climb check he must roll 5 or under.

Celwin passes through two hexes without incident (no checks necessary), but in the third hex he is attacked by a green tiger. After striking some good blows, in the third round he takes damage, the tiger batting him around like a rag doll. He must now roll a falling check. Bad luck! He rolls a 6. He has now fallen 50' and must save vs. paralysis. He makes the save, managing not to take major damage on his plummet down. He now makes a second climb check without the bonus for being heavily secured. He still receives the bonus for being on Level 1 of the jungle and for being unencumbered. So he must now roll a 3 or under. His bad luck again, missing with a 4! Now he falls 100' meet and fails his save vs. paralysis this time, taking 2d6 damage (7 points of his 10 remaining hit points!).

He now makes a third falling check. This time he just passes with a 3! So, although his head is bloodied from a terrible blow against a tree, he is now clinging to a branch at 150' lower than he was originally. The tiger roars above him in frustration looking for a route down as Celwin shakily pulls himself to his feet, wiping blood from his eyes...