Pros and Cons of giving my party a spell based on the Portal Gun from the Portal video game series? [closed]

Question

I'm considering giving my party's mage a Portal Spell as a way to spice up our campaign. The catch is they can only use it twice per day, the target surface has to be flat, clearly visible by the caster, and less than 40 feet away. The portal only lasts about 2 minutes, is 5 feet in diameter, and takes 6 seconds (one full round of combat) to cast for both ends. They can also only have one pair active at a time, and the portal remains completely solid until a second one is activated.

I'm trying to figure out how this would affect the overall game's development. I want this spell to be very useful in some situations, but not become the solution to absolutely everything and hence make the game boring. Since this is a very versatile and mind-bending spell, I wanted to see what some others thought before giving to them (I can always take it away, but I'd rather not have to).

Here's some things it would make trivial:

• getting across a small valley, treacherous river, or spike-filled pit.
• getting onto high surfaces that have a roof over them.
• moving heavy objects that the players can push into the portal. Squash the enemy!
• it has line of effect through it, so you can shoot arrows, cast spells, and thrown things through it.

Does this spell seem ridiculously over-powered? Should I add some additional catches, or give it to them as is? What creative uses that I'm not thinking of might it have?

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NOTE: I'm tagging this system-agnostic because my group uses free-form roleplay as our system: we have nearly no stats whatsoever and I resolve things as I see fit, even though I try to be as consistent, fair, and realistic as possible. I suppose they would be around level 3 in D&D 4.0 so you can get an idea of how powerful they are, but please don't let that have any significance other than telling you they don't have super-ridiculous spells yet. :D

Watch this video for a quick demonstration!

Answer 1

Pros

The challenges facing PCs suddenly change: instead of using resources to cross that bridge or strategically positioning an enemy under a heavy object and then tipping it, they can use the portal spell and their environment to play with physics. If you want to give them this spell and truly interact with the environment, I'd not set a hard limit on its uses per day, only just requiring a party resource to manifest. Then players are actively encouraged to manipulate the environment with portals, a way to spectacularly express agency that would otherwise require elaborate set pieces on your behalf.

As players use the portaled world more, they are forced to articulate that world more, increasing immersion and fun.

Cons

They become quite a bit more "powerful." The ability to manipulate the environment changes challenges facing the party. Instead of thinking about how to kill a particularly pesky sentry, cross a uncertain bridge, or what have you, they start thinking with portals. While I think that this presents a welcome change, it is the kind of magic that shapes the game around it.

I would absolutely support a magi in Ars Magica researching a spell like this (not least because an omni-portal would be remarkably difficult for them to cast), but mainly for the character-defining element that it provides. I would be much more hesitant to do that in a 4e game that cares about tactical balance, because it obsoletes so much of the prepared material. For a freeform game and players that enjoy this sort of thing, I would tend towards my Ars Magica interpretation.

Summary

This spell is a game changer. Make it cost real resources instead of a 1/day limitation. It will change the tactical modes of thinking of your players and promote environmental immersion. It will also render most "mundane" challenges moot. If your players enjoy mundane challenges, it's too powerful. If your players find them frustrating or speedbumps, by all means, allow them their awesome-spell.

Answer 2

Given the parameters of the spell, then it's not as OP as it might appear, though it probably is a bit higher level than they'd have at this time.

The first parameter that I think needs to be defined is offensively, does the defender get a save? And second, do the portals stay in existence when they are out of sight? (As Portals don't persist from room to room, I put that LOS existence to sort of represent that)

Second, the twice per day limitation- is that two placements? Or is that two pairs of placements? A distinguishing fact.

And third, distance between portals. There is a range given, but no distance limit between the two portals. If you cast a portal 40 feet in one direction, then 40 feet in the other direction, that's 80 feet. And that's without moving- which becomes an issue given the 2 minute duration.

Given those parameters, and the parameters that you've already given, this is not that dissimilar to Dimension Door from PHB162, which is a daily, 6th level, Personal spell.

The differences:

1. The Portal spell is not personal. Pros for your version: Allows a portal effect, and others can use it. Cons for your version: you have to be able to move to use it (A big deal in dnd4e, as teleportation without movement doesn't provoke opportunity attacks).
2. You maintain inertia with the Portal spell (presumably).
3. The Portal spell can be cast at range.
4. The Portal spell has a duration.
5. The Portal spell (conceivably) has a shorter range. Dimension door has a range of 100 feet.

Given these differences, the Portal spell isn't really that OP- just higher level; I'd think probably 10th+ normally.

In the end, it changes some problems, while opening up others; it will also change your preparation as a GM, as your obstacles will have to be built in a more Portal-like manner. It also opens up some really cool uses; you can make things appear impossible, but solvable using the Portal spell.

The daily limitations help in reducing the dependency on it, as would making it a ritual, so that it takes time to cast, and materials, rather than just making it daily. Indeed, you could start out with it a ritual, to see how the effects work in game, and something that they find later could remove that limitation/make it a non-issue if you see that it's working well, and conversely, reduce/remove their access to the materials if you need to tweak it to be less readily available.

Answer 3

Just make a "Portal Device" minor artifact they stumble across. That'll solve a lot of problems with balance, while it can be useful, it's an artifact and everyone and their mother will come gunning for it if they flash it around too much. And you can conveniently remove it that way if it turns out to be too powerful and/or hard to work around.

With a hidden drawback of having a chance causing temporal distortions on use that can potentially draw extra-planar creatures to them or transport them unwillingly to a random plane.

Set up a range limitation that portal entrances need to stay within 100 yds of the device or they wink out (or smaller if you wanna fine tune the control)

Answer 4

Since you resolve things as you see fit, the power level of such a spell is going to be pretty arbitrary. However, if your player characters are about as capable as a group of 3rd-level adventurers in Dungeons & Dragons 4E, this spell is much more powerful than such characters can typically perform. This is doubly true if the portal can be placed below an unwilling sapient target, or if it could be put at the bottom of a lake or other body of water and the force of motion carries through.