"I can't pull the pole back out? ... Hmm... Okay gang, let's dam up that river we saw earlier so it flows in here. The water will teleport over when it touches the portal, which means it will constantly mount in pressure on the other side. We'll come back in a week with water breathing spells, after it got so bad it must have shattered something and leaked down to ambient pressure levels. Anything over there will be dead from the core-of-the-planet level pressure, it'll be easy looting."
I pulled a magic portal in one of my last sessions. The party's thief jumped through one while the rest of the group was negotiating with an orc warband. The orcs saw this happening and jumped on their feet, they knew that the portal was connected to a plane of Death... The PC was saved, but a couple of rounds for the party was days for the thief... who returned in a comatose state. The thief player decided to add a flaw to his character, an obsession to the otherworldly dimension he saw.
When my last long-running 5e campaign got to high level, I gave the fighter a magic bow that could be used as a portal gun. It was a good way of giving them some cool unique powers to help keep up with the spellcasters throwing around 9th level spells.
I LOVE the portal countdown. So fun when portals lead to an immediate scenario. It’s hard on players to ignore the meta knowledge that the pc on the other side of the portal is in combat, so this offers a fun and tense solution.
I plan on using a portal trap against my players. It's pretty simple actually, the portal is in a normal looking doorway in a room that has doors on both ends if some kind. Going through the doorway without checking it for traps portals you to the other end of the room that you entered from. The baddy in the office on the other side is then alerted that someone tried to walk in. If the magic is deactivated it works just like a regular door.
There's one portal metaphysic I'm surprised to not see, if only because it's how it works in science fiction shows like Stargate SG-1. I think of it as a "delayed buffer" system. What goes into the portal on one end gets put into some immaterial buffer of sorts and does not come out the other until it's fully entered the portal first. Someone sticking a stick through the portal may or may not be able to pull it back, but either choice can be consistent with either one- or two-way portals, since it's not interacting with the far side of the portal at all until it's fully committed to entry.
4:27 You have a line in the script present in the closed caption and missing from your audio. When you are talking about the "area of affect teleporting gateway portal", in the metaphysics section, your CC says "and only have objects vanish if they are completely within that threshold".
Yeah, I played with this idea some years ago in a campaign I called "Cityscape" where any door could lead to any other city, or ruins of any other city, to ever exist, have existed or will exist. Within the city there were also these mazes and traps where explorers looking for treasure could be caught in time-loops or dropped into the middle of a cataclysm from which they had to find another doorway to escape (Or, in one instance, the PCs used a time portal to travel back to a point prior to one of them being killed). Took inspiration from Planescape and A/State. In one of my Planescape games, a player got sucked through a portal into another plane and the others had to find him, so I ran that player for a solo session while the other PCs were finding a way to get to him.
I once had fun with multiple portals in a room. There was a font that when full of water and had gemstones in it made portals go through to new areas, else the portals would just lead back to the same room, or act solid and unable to pass through. Of course, the tendency for players is to grab the loot and not link that they needed it in the font to work. One time I did this, we had a cleric who saw the font glowed magic and proceeded to drain the font for holy water and divvy up the stones for everyone else. For a while I was worried they were not going to work out the link, so I sent a couple of creatures through one of the impassable portals the other way, angry because the portal from their side didn't go where it was supposed to, and came to find out who had been mucking around, They made that clear they were upset at the players and they did something wrong. It clicked pretty soon after that. Either way, you are right, portals can be fun. I need to use them again sometime.
Man, you really dig deep on this stuff! One of my favorites was the transformational portal:). But I guess people might be too sensitive for that gimmick these days!
Another good one is C3 The Lost Island of Castanamir, which is full of one way portals where going back takes you to a different room than the one you had arrived from. When we played it, I probably hadn't given enough thought to the "metaphysics", and my players went wild reaching through and then tossing a crumpled up note with an alphabetic code back towards them so if they found that note later they would know where that portal connected to. The actual adventure is a little bland and empty (I've run it twice and it was a bit unsatisfying each time) but I've always loved the weirdness of the wizard's home with its dimensionally disconnected rooms.
