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Encounter: The Skeleton Bridge

January 28, 2019

Another extra from the Fantasy Trip Adventures campaign . . .

“Waste not, want not.” It’s a great life philosophy, but one that takes on disturbing overtones when dealing with necromancers. The skeleton bridge is an accidental trap devised by a long-dead necromancer dabbling in areas he didn’t quite understand.

The skeleton bridge is intended as either a reasonably quick encounter or an add-on to a larger adventure. It’s especially useful for a GM who wants to keep the heroes from leaving their current environs.


Lots of necromancers dream of discovering the secret of the whole “make an undead army rise from a graveyard” thing. It’s flashy and cool! And in the necromantic realm, bones are often used as a decorative motif; thrones of bone are always fashionable, but designers can make lots of other interesting structures out of old skeletons.

However, would-be researchers need to be careful when combining bone-based infrastructure with skeleton-army experiments, or else the result might just be a bridge that self-destructs.


The core concept of the Skeleton Bridge is, unsurprisingly, a bridge made of bones. This should be as large as needed to be interesting, while small enough to keep the core danger of the bridge exciting. A good rule is one megahex per hero, so good layouts for a party of six PCs could be either two megahexes wide by three megahexes long, or (for more danger) one megahex wide by six megahexes long.

The bridge has a trap on it that causes it to animate skeletons. Unfortunately, the enchantment uses the components of the bridge itself to create its army. Thus, the more the heroes fight on this bridge, the less stable it becomes.

As the heroes get within one megehex of the bridge, it creates a number of skeletons (In the Labyrinth, p. 88) equal to the number of heroes approaching. (Stats are left to the GM’s imagination to provide an appropriate challenge; each skeleton is armed with a bone “club.”) If the bridge is the same number of megahexes as the heroes, then that first wave of skeletons is easy: one skeleton per megahex. These fiends are conjured from different areas of the bridge, randomly placed in their “summoning” megahex on the bridge. Keep track (privately) of how many skeletons each megahex creates, since that segment of bridge gets weaker as a result of each summoning. The skeletons then move and attack the heroes as normal.

At the beginning of each turn spent on a megahex that has created a skeleton, the hero must make a saving roll equal to the number of skeletons the megahex has created plus the number of non-skeleton human-sized beings that are on the weakened megahex. (GM’s discretion for really heavy or light entities, but the skeletons themselves are too light to worry about.) Thus, if a megahex has summoned two skeletons and has three heroes on it, then each hero needs to make a 5/DX save. Acrobatics reduces this roll by one die, as normal.

Failure means that the hex (not megahex) the hero is on collapses into the void below; it is now considered an open hex. A critical failure means the entire megahex has collapsed. Any entity that is on a collapsing hex or megahex can make a 3/DX save (again, adjusted by Acrobatics) to shift one hex to safety (if such exists). Skeletons don’t need to make rolls on the bridge – they won’t trigger a collapse themselves – but they also aren’t smart enough to try to save themselves if they’re on a collapsing hex.

Once a skeleton is killed, the bridge summons another skeleton to replace it, from either the “strongest” part of the bridge (if the GM is kind) or a random megahex of the bridge (if the GM is cruel). The bridge responds to the laws of physics as expected, so that if a hex (or megahex!) is completely unsupported by surrounding hexes, it falls into the void. Thus if the bridge is 1 x 5 megahexes and the first and fifth megahex collapse . . . well, hopefully no one important is on those center three megahexes.

The bridge will keep summoning an appropriate number of skeletons – one per living target – until the bridge completely collapses (no more bones equals no more skeletons) or until the heroes move beyond the one-megahex summoning range of the bridge. Although it shouldn’t become vital to know, each megahex has enough bones to summon about 20 skeletons. Summoned skeletons will not pursue beyond this summoning area (so, at most, one megahex beyond the bridge proper). Of course, if the heroes move back to within one megahex of the bridge – say, by wanting to return the way they came –they must encounter the same bridge. (The bridge will repair itself to full strength over the course of months if it does not completely collapse, but that’s beyond the timeframe of most adventures.)

Although players may figure out what’s going on themselves (it’s not that complicated), the actual mechanism by which this is all happening – “bridge gets weaker as skeletons are summoned” – is not obvious, and requires a roll using Alertness or Detect Traps, or some similar method of determining specifics (Remove Traps does not help make this situation safe).


How dangerous this encounter is depends on what the bridge is crossing. If it’s over a gentle river that’ll float plummeting adventurers to new and interesting parts of the dungeon, that’s annoying but not terrible. However, it’s much more dangerous if it’s over a chasm or inky void.

It’s up to the GM how ruthless the skeletons are programmed to be. It’d be particularly cruel if the skeletons use tactics and numbers to keep the heroes on the bridge as long as possible, or to try to push interlopers off the bridge . . .

As a quick adventure, put something the heroes desire on an islet (a treasure, the McGuffin to break the curse, etc.), with the skeleton bridge the only way on or off the island. Thus the heroes need to face the skeleton bridge twice (once each way).


If the heroes tend to fight to the death at every encounter, then they’re bound to have a bad day. The most likely way to survive is to realize the nature of the problem and then move quickly (and diversely) across the bridge to the other side. Alternatively, it’s entirely possible for the heroes to force the bridge to collapse, then rely on some spell or ability to fly across.

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