I recently ran a fight in my Really Wild West campaign, using Starfinder rules, that took place atop a series of spinning, moving, shifting gears. Overall, it was big hit.
Now, this was made much easier by the fact that one friend of mine made these big green gridded disks from flower/cake foam (to use as hills and such), and other got this spinning, sliding lazy susan tabletop. So all I had to do was tell folks the disks were big bronze gears, spin and turn them (they both rotated on their own axis, and spun around each other at different speeds), and players could rotate the whole map if they needed to see what was on the far side of the gear-pile.
I warned people that the mechanism was so complex as to be essentially unpredictable, so while I tried to follow some basic rules on how things spun and moved, if I messed up players knew that randomness was intended. While the gears were officially in constant movement I just relocated them at the end of each round, so players always had a chance to react to one position before they formed a new one (and, after all, realistically the characters are in “constant motion” as well).
On top of the big moving gear platforms, there were two sets of “control cogs,” parts of a Babbage system that controlled the movement of the gears (orange markers), and the actions of the constructs defending them (green markers). The mechanic in the group managed to get access to those things, though it wasn’t easily, and one-by-one shut down the constructs while their allies used mobility (including good Acrobatics or Athletics checks and actual mobility to avoid attacks from spinning gears as the dodged about), flight, and climbing to move around.
So, this encounter had fairly normal combatants, but a lot of other things going on as well. In fact I kept the combatants pretty straightforward (well… one had a steam-pressure triphammer than could boost for multiple rounds to gain more and more bonus dice to its next attack) just so I wasn’t throwing too much at the players.
I’ve done similar things with moving elements before–fighting on rafts in rivers choked with floating logs, conflicts on trains both mobile and stationary, running battled through tunnels with teleportation gates, stampedes as hazards with big rocks to hide behind and every other space counting as an attack of opportunity as you try to avoid being trampled–but I think this is the most complex and multi-moving-part encounter I’ve done. And my players are all veterans of gaming and general and, at 9th level, this campaign and these characters in particular.
And it’s fairly easy to spice things up with doing so far as to have two Jedi battle it out on rocks bobbing along streams of lava with guard skiffs flying by. A battle behind a waterfall makes everything wet, and drowns out all noise. Defending a wall gives all the PCs cover–or all the PC’s foes cover, depending on which side of the wall they are on. A cliffside fight is all about climbing up, down, and sideways rather than running N, S, E, and W. Fights on frozen ponds, or in hurricanes, or in grass fields that stand 12 feet tall — not only do these things give the players a new experience, it can make various class and ability options they take worthwhile. Who wants to move freely through natural terrain if there isn’t the occasional thorny bramble covering 13 of the map, with grig archers shooting out of it?
You don’t need to shake things up in every battle, but just a few props now and then, or a different kind of terrain or local hazard, can help a specific encounter be memorable.
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