D&D 5E D&D Adventure in an Asteroid

M.T. Black

I'm thinking of setting a D&D adventure inside an asteroid (specifically in the Tears of Selune). I imagine there would be gravity, heat and atmosphere effects to contend with. Anything else that would distinguish tunnels in an asteroid from a dungeon in the ground?

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Possibly a Idiot.
Hopping from Asteroid to Asteroid. Which means dealing with the rotation and drift of the asteroids, occasionally colliding into another asteroid, and waiting until the asteroids are lined up in the proper direction to make a jump.

Also throw in liberal amounts of Spelljammer stuff. Space Hippo-men with Guns will let the PC's know this isn't their typical adventure really quick.

Capn Charlie

An easy way out is to say the tears have some kind of magical gravity, just so the basic game rules function as written. For fun, give the characters some sort of barsoom-ian effect, from lower gravity, like advantage on athletics and acrobatics to jump or climb, double move speed, double jump distance, something like that.


Dusty Dragon
I really wouldn't run a game inside an asteroid. The lack of gravity would make dice rolling extremely difficult for one, not to mention the long travel time, harsh environment etc. If your home isn't suitable for running a game, ask one of your players maybe?

Oh - *set* inside an asteroid. Carry on.


Part of the question is - do you want to deal with no gravity? I think it could be fun ... for a while. I could imagine a fight where if you weren't properly braced shooting a bow meant you propelled yourself backwards, swinging a sword would make you twirl, etc. You could make it an asteroid with high iron content and give people magnetic boots to compensate (or just special magic boots). Of course any magic that let you fly would also probably fix the issue. In addition, if there is no gravity there is no up or down.

Obviously you're going to have a total lack of light, but what about temperature and atmosphere? It's a magical asteroid so you could hand-wave it or rely on magic/potions. Could be kind of fun if the group has to cross an anti-magic zone. Although in a vacuum, you don't really radiate heat so I'm not sure how to handle that. If you wanted a realistic response google it. Basically you would only survive for a few rounds since trying to hold your breath would cause your lungs to explode. Oh, and the spit on your tongue will start to boil. :eek:

The caves would likely be similar to what we see in lava tunnels, so no stalagtites/stalagmites

The monsters I would populate an asteroid with would probably all be aberrations or oozes. Nothing says space like tentacles and too many eyes.

Anyway those are my suggestions. Sounds fun, I may have to steal the idea some day!


First Post
The Return to the Tomb of Horrors adventure took place in a very inhospitable realm that had some of the properties of outer space. That could be a good source of guidance.


Dusty Dragon
seriously speaking... don't think about the physics *too* much. Unless this is a serious sci fi game, if the heroes are there it's going to involve magic... and maybe asteroid in a D&D world have *far* different properties than real life ones. If you want your asteroid to have air, funky (as opposed to almost non existent) gravity etc etc, go for it!


If you're running it using miniatures and a battlemat, do the wraparound map trick - everything that goes off one side comes on the other. Use the excuse of it having its own center of gravity to explain why missiles and spells don't go flying off into the void, so can come looping back around to literally get the PCs in the arse. Set up several small maps using this trick, and then have them draw close during the fight, so people can jump from one to the other. Possibly limit lines of sight so to represent the curvature of the asteroids.

That's on the outside of the asteroids of course. Inside, if you want complication, make it so it's constantly rotating, and at any given moment (or at start of the turn), everything can suddenly move 90 degrees or so, make the floor and roof the walls, and the walls the roof and floor. Anyone native to inside the asteroid would have everything fastened down, and have some sort of climb speed to negate the worst of it.

Have a zero g fight. This easier than it sounds - everyone simply has a flight speed (with hover) and everything that has a physical or force damage type automatically has a push effect. Watch PCs and enemies go flying around like mad.

one thing to keep in mind asteroids tend to be small.

If you decide to use a rougly sperical asteroid you might want to try to draw the dumgeon map on a ball.
becouse coridoors and rooms might turn out to link up around ther equator.

Epic Threats

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