In “The Joy of Extradimensional Spaces,” an adventure by Michael Polkinhorn in Candlekeep Mysteries, the PCs discover a portal to an extradimensional space, go through it, and become trapped on the other side.
This is a classic trope, and for good reason. Perhaps the most memorable and well-known version are the arches of mysterious mists and the green devil faces of The Tomb of Horrors, but I’ve run some variation of this gag countless times.
Often, of course, PCs will also encounter mystic portals and strange gateways of coruscating energy that aren’t one-way affairs. But they won’t necessarily know that. And even if they don’t suspect a trap, the unknown threshold beyond which they cannot see is quite likely to inspire endless amounts of paranoia.
So, either way, the day will likely come when you hear some variation of: “Okay, let’s send Kittisoth through first to check things out.” Or: “I stick my ten-foot-pole into the portal and pull it back out.”
First: Know your metaphysic.
What does happen when you stick something halfway into a magical portal and then pull it out?
A few variations:
- No problem. It’s just like a doorway in space, even if the field of energy blocks your line of sight. (Perhaps you might even be able to still hear what’s on the other side.)
- You can’t pull it out. Once an object has gone partially through the portal, the only movement allowed is forward through the portal. If you pull back, it will feel as if the object is “stuck.”
- That’s incredibly dangerous. You can pull back, but you’ll only pull back the portion that’s still on THIS side of the portal. (Make sure you walk through these portals with confidence.)
- That’s not possible because as soon as any discrete object or creature touches the surface of the portal, it instantly vanishes and reappears on the other side. It’s more of a “touch here to activate” effect than it is a literal gateway. (This one can get tricky: If I prod it with a pole, do I vanish? Can I tie a rope to something hundreds of feet away, toss one end of the rope in, and have the whole thing go through the portal? What if the object is bolted to the floor? Or is a huge tree and the room on the other side is only 10’ x 10’? But, conversely, if I touch it with my hand do I disappear while leaving my clothes behind? One way to simplify this is to create a “threshold” before the portal – a misty arch, a field of energy, a penumbral aura, the entire room that the portal is in – and only objects within that threshold vanish when the portal is touched. Your choice whether to have something straddling that threshold get severed at the threshold or if the whole object remains even when touching the portal. But I digress.)
You want to have a clear understanding of this, because the players will want to experiment with the portal to figure out how it works / whether or not it’s safe. They’re going to come up with all kinds of crazy testing schemes, and you’re going to want a clear conceptual framework for consistently ruling what the outcomes of those tests will be.
I’m of the opinion that this metaphysic should feel consistent with the portal’s behavior on the other side: If it’s a one-way portal, for example, then you shouldn’t be able to stick things through the portal and then pull them back. (In other words, you want to play fair and reward players who take the effort to engage deeply with the scenario.)
Second: Use a portal countdown.
When the PCs send a scout through the portal, don’t immediately describe what the scout sees. Instead, stay with the PCs that remained behind: Describe the scout going through the portal, disappearing, and then… what do you do?
Keep track of the number of rounds it takes for each of the other characters to go through. Then, once they’ve all done so, you can flip to the other side of the portal and accurately play out events on the other side.
So, for example, Kittisoth walks into the portal. The other PCs wait a couple of rounds and then Edana sticks her ten-foot-pole through. Unable to pull it out, she sighs and steps through on the next round. Everyone else then nervously follows on the fifth round.
Now cut to the other side of the portal: Kittisoth emerges into a goblin ambush! Roll initiative! On the third round of combat, Edana’s pole sticks out of the portal. On the fourth round, Edana walks out. On the fifth round, the other PCs join the fray!
Even if there are no immediately “interesting” consequences from using the portal countdown (e.g., the portal emerges into an empty room and Kittisoth just patiently waits for everyone to join her), the experience is still immersive and tantalizing in its paranoia: What is happening on the other side of the portal?
When there IS something interesting happening on the other side of the portal, the experience of seeing the other side of the timeline (e.g., Edana’s pole sticking out of the portal) is a ton of fun.
What if all the PCs don’t come through? That’s fine. Run a couple rounds of the portal countdown in “combat time,” but when it becomes clear that some or all of the remaining PCs aren’t going to follow Kittisoth blindly through the portal (“She was supposed to come back!”) simply ask them how long they’d wait, note that on the countdown, and then cut to the other side of the portal.
Should I have players leave the room? If you’d like. I’ve not generally found it to be necessary and, as I mentioned, I’ve found the audience stance of seeing the other side of the timeline to be fun. But I’ve also been given to understand that the experience of going into another room and waiting while your fellow players join you one by one can also be mysterious and fun. Play it by ear and get a feel for what works.
(If you’re splitting the players up anyway, you may also want to just go back and forth between the two rooms each round instead of using a portal countdown.)
What if it’s not a one-way portal? This technique works best with one-way portals because the events on one side of the portal are generally firewalled from the other side of the portal, but since the players don’t always know if the portal is one-way or not, it can also be effective to use the technique regardless. (If nothing else, it means you’re not tipping your hand when they do encounter a one-way portal.)
But what if, for example, Kittisoth simply walks back through the portal?
If that outcome is quite likely, of course, then you don’t want to use the portal countdown technique in the first place. Or use it in a modified form. For example, if Kittisoth’s intention is to walk through the portal and then immediately turn around and walk back and there’s nothing on the other side that would prevent that from happening, you can just run it normally. Or you might take Kittisoth into another room, describe what she sees, and get a sense of her intentions: If it looks like she’s going to explore a bit – or get cut off from the portal by the goblin ambush – then you can go back and run the portal countdown.
But if you are using a portal countdown and Kittisoth comes back “early” (i.e., before all of the declared actions on the countdown have played out), that’s just fine. You can simply retcon the rest of the countdown; those actions belong to an alternative version of reality, I guess.
(The portal countdown is basically an extended form of declaring an intention. It’s similar to combat systems in which everyone declares their actions at the beginning of the round before resolving them in initiative order: If someone declares that they’re going to run down an open passageway, but then the passageway gets blocked with a wall of stone before they can take their turn, they’re not going to just mindlessly grind their face into the wall like a computer game NPC with bad pathing. They just won’t take the action.)
What about other continuity issues? Keep in mind that premature portal returns aren’t the only contradiction of continuity you can run into. For example, those on the far side of the portal might use a telepathic ability to contact their comrades. Or Kittisoth might grab the end of Edana’s pole and yank her through the portal.
Again, that’s fine. Just end the countdown and begin resolving actions normally from that point. (Which might even include starting a new portal countdown depending on what’s happening.)
Similarly, you generally pause the countdown and begin resolving actions on the far side of the portal when everyone has either gone through or definitively decided NOT to go through. But actions on the near side of the portal can also trigger this decision earlier: For example, if it’s Edana who chooses to use a telepathic ability to contact Kittisoth (assuming that she can do so), you’ll need to pause the countdown and resolve Kittisoth’s side of the portal.