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Old 04-28-2015, 04:37 PM   #21
Grouchy Chris
 
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Default Re: Building permanent magical traps with GURPS Magic

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Originally Posted by David Johnston2 View Post
Create Fire is an enchanted area that deals direct damage.
You can't permanently enchant an area with Create Fire. Look at the section on "Enchantments Without Items" on p. 18 of Magic, and the Item text for Avoid, p. 140. That's what I'm talking about.

Quote:
But I don't really see the issue. If you want to make a brass dragon's head that can puke fireballs at anyone who walks through a door without bearing the Master's Sigil, then some enchanter did some custom work. That PCs couldn't duplicate it without a lot of research doesn't really matter.
I have what I consider a good reason for not just handwaving it and saying "The trap does 2d6 fire damage to anyone in area A if someone enters the trigger area B." That reason is player options. Using the standard magic system allows the players a broader range of ways to defeat the trap.

Let's say we're working with an alteration of the rules that lets me cast a permanent Fire Cloud area enchantment along with a Link spell that determines when it activates, and I place it in the path of the PCs. Then the area is magic, and so anyone with Magery gets a roll to detect it. Analyze Magic will let them find out what enchantments are on the area, or a Thaumatology roll will identify the spell if they see it in action. They can protect themselves against it with Resist Fire, or negate its operation with Counterspell. They can permanently disable it with Remove Enchantment. They can make a Thaumatology roll to determine that a Fire Cloud enchantment requires a ruby, then cast Seek Earth to find the ruby and remove or destroy it. If the trap is powered by a powerstone, they can find that and remove or destroy it.

And here's the really important part: if the magical trap system works using standard rules that are published for all to read, then clever players can figure all of this out for themselves, and know that it will work,, because these are all things that would work under the standard magic system. They can also come up with approaches the GM hasn't even thought of. That gives the players a lot more choices for how do deal with things, and I like giving my players the chance to succeed by being clever and figuring things out.

On the other hand, if I just say, "magical trap, take 2d fire damage, it just does what it does" then they are operating much more in the dark and don't know what their options are. They don't know whether there's a way to disarm or disable the trap at all, and might spend half the game session fruitlessly contriving one attempt after another to change something that can't be changed. That makes for a frustrating game for everyone. If I make a habit of using such traps, then the players eventually learn to just take it and move on. That's a whole lot of potential play shut down.

And maybe I do want to put a magical hazard into play some time, and say that it just does what it does, and your normal approaches to dealing with magic don't work. That's going to stand out a lot better as HEY THIS THING IS WEIRD AND DIFFERENT AND THEREFORE MAYBE PRETTY IMPORTANT a lot better if everything doesn't work that way.

So that's why I'm looking for magical trap rules that work this way.
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Old 04-29-2015, 07:02 AM   #22
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Default Re: Building permanent magical traps with GURPS Magic

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Originally Posted by Grouchy Chris View Post
You can't permanently enchant an area with Create Fire. Look at the section on "Enchantments Without Items" on p. 18 of Magic, and the Item text for Avoid, p. 140. That's what I'm talking about.



I have what I consider a good reason for not just handwaving it and saying "The trap does 2d6 fire damage to anyone in area A if someone enters the trigger area B." That reason is player options. Using the standard magic system allows the players a broader range of ways to defeat the trap.

Let's say we're working with an alteration of the rules that lets me cast a permanent Fire Cloud area enchantment along with a Link spell that determines when it activates, and I place it in the path of the PCs. Then the area is magic, and so anyone with Magery gets a roll to detect it. Analyze Magic will let them find out what enchantments are on the area, or a Thaumatology roll will identify the spell if they see it in action. They can protect themselves against it with Resist Fire, or negate its operation with Counterspell. They can permanently disable it with Remove Enchantment. They can make a Thaumatology roll to determine that a Fire Cloud enchantment requires a ruby, then cast Seek Earth to find the ruby and remove or destroy it. If the trap is powered by a powerstone, they can find that and remove or destroy it.

And here's the really important part: if the magical trap system works using standard rules that are published for all to read, then clever players can figure all of this out for themselves, and know that it will work,, because these are all things that would work under the standard magic system. They can also come up with approaches the GM hasn't even thought of. That gives the players a lot more choices for how do deal with things, and I like giving my players the chance to succeed by being clever and figuring things out.

On the other hand, if I just say, "magical trap, take 2d fire damage, it just does what it does" then they are operating much more in the dark and don't know what their options are. They don't know whether there's a way to disarm or disable the trap at all, and might spend half the game session fruitlessly contriving one attempt after another to change something that can't be changed. That makes for a frustrating game for everyone. If I make a habit of using such traps, then the players eventually learn to just take it and move on. That's a whole lot of potential play shut down.

And maybe I do want to put a magical hazard into play some time, and say that it just does what it does, and your normal approaches to dealing with magic don't work. That's going to stand out a lot better as HEY THIS THING IS WEIRD AND DIFFERENT AND THEREFORE MAYBE PRETTY IMPORTANT a lot better if everything doesn't work that way.

So that's why I'm looking for magical trap rules that work this way.
And why do you think one negates the other?!

Glossing over the very tiny specific ways things are possible on your world doesn't have much with allowing your players to be clever and have fun on your game, and that's why I say you're (imo) paying too much attention on the wrong part.

The important part is the base Spell and that's pretty clear on the basic rules most of the times. Simply use the base spell rules and dynamics to determine those guidelines you said yourself you want to keep possible to your players to deal with and that's it.

Using your 2D fire spilling trap example:

Unfun Way

Why it works: Just because.
How it works: Cosmically and don't have any way to know or deal with it cleverly.

Good way

Why it works: Just because.
How it works: As Fireball spell.

Since it's mechanically a Missile Spell (Fireball) they can "Deflect Enerngy" it; They can use "Resist Fire" 2 to ignore its effects; They can "Missile Shield" against it...and so on.

It doesn't really matter much for your players if the rules would normally allow or not such enchant, as long as you keep it consistent with how things work inside the magic system in your setting and what they could expect from it.

On the "Fire Cloud" case, all the mechanics you cited are preserved if you consider the spell nature and work with it. Why would you not allow a Magery or Thauma roll if you just decided "This area is a trap and covers with Fire Cloud when triggered!" ?!? It's still magic and should work as magic, more specifically the base spells that originated.

Even if you create completely new spells, if you keep it consistent with base mechanics, your players will be able to deal with it.

Last edited by T.K.; 04-29-2015 at 08:33 AM. Reason: wrong is 2 stronk
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Old 04-29-2015, 09:53 PM   #23
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Default Re: Building permanent magical traps with GURPS Magic

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Originally Posted by hal View Post
I'm curious - just how "lethal" do you want your magical traps?
Everything from mildly annoying to "the problem with Tomb of Horrors is that it's too nice to the players."

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Originally Posted by hal View Post
Create Gate:

Use of this spell permits the caster to set the conditions under which the gate shall operate.
Ah, that's good. The spell comes with an effective built-in Link, and you've exploited it well.

[...]

Quote:
Net result? A stone trap with two stone pillars as ammunition for the trap. It could probably be done with one stone pillar - but what the heck, if one is good, two is better ;)
I would probably want to rig it with just one pillar, to keep it simple. Also, nitpick: Grease is an area spell, and it can be used to permanently enchant an area, but I don't see how stone pillars count as an area. I don't think it's really necessary anyway -- if there's nothing hold it up, the pillar is going to move, Grease or no Grease.
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Old 04-29-2015, 11:06 PM   #24
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Default Re: Building permanent magical traps with GURPS Magic

Hi Grouchy Chris,
Yes, Grease is an area spell, but can be applied selectively to the stone pillar's faces - all four of them one at a time. So yes, it can still be applied to the stone pillar in order to permit it to slide more easily.

Now for this next trap, you're going to need to take a ruler and balance it on your finger to get the idea of how it works. Picture the ruler as being disguised as a stone corridor's floor. Half of the ruler (Stone beam actually) hangs over air such as a cavern or something. The other half of the ruler (from the 6" mark to the 12" mark of the imaginary ruler), rests on a stone lip. Now imagine a party of player characters entering into a corridor that is dimly lit - but for a faint magical glow of light - as if enchanted with the light spell. Clearly, any mage with magery has the opportunity to sense that the floor from the imaginary 6" mark towards the 1" mark is magical. So you give them something to see - the "light spell". As they approach the center of the beam of stone (the 6" mark on our imaginary ruler), nothing happens. As the party passes the 6" mark and is heading towards the 5" mark, they are beginning to upset the balance of the fulcrum. By the time they make it to the 3" mark, the floor is starting to tilt downwards...

THAT is when the Link spell activates the Grease enchantment. The player characters will be penalized by an initial DX-2 for the Grease spell, but an additional penalty for uneven ground (in the literal sense!). Now - as the 12" mark of the ruler begins to rise, it will stop against the ceiling if it is only 10' up from the floor right? So the GM has to remember that the ceiling at this point will be HIGHER than 10' to accommodate the rising portion of the floor.

Net result? Once they reach the tipping point - if they don't start to run back, they are doomed to slide down the now tipped greased flooring into the chasm/drop/room/gate etc waiting for them at the end.

Knowing how time causes things to bind together or gravity can cause things to fuse together, one needs to insure that the fulcrum point itself is greased at ALL times. This way the fulcrum itself, and the apex of the point the fulcrum rests upon - don't bind together.

Other ways of using GREASE as a spell is to use it on a ramp. As players walk onto it - the delay in activation due to the Link allows them to walk fully into the danger zone. As you might guess, a ramp with spikes at the end of the ramp is not a healthy thing for the players to run into. Now to be really nasty? Have the ramp make a 90 degree turn midway down so that the person falls OFF the ramp etc.

GREASE is a NASTY spell to use as a gravity assist trap.
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Old 04-29-2015, 11:17 PM   #25
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Default Re: Building permanent magical traps with GURPS Magic

Not that the GM wants to do this, but one trap I used on my players back around 1983 or so, was this one (using The Fantasy Trip).

Player one had a favorite player character that he lost to an enemy who was trying to capture player #1's character. The NPC succeeded. So he placed player character #1 into a dungeon. Enter three more players into the campaign, plus player #1 playing his second player character. Player Character #2 had a twin brother NPC #3. Then we had player #2 with player character 4, player #3 with player character #5, and player #4 with player character #6. Got that?

Ok, so player character #2 is trying to rescue from prison, player character #1. They find what looks to be player character #1 laid out as if dead in an open stone casket/crypt with a crown and a pendant hidden under the clothing. The Crown as a Suspended Animation magic item. When player character #2 removed the crown from sleeping player character #1, player character #1 was retained by the GM instead of reverting to the control of player #1. I informed the group that player character #1 being played as an NPC was attacking them. The player yelled at me "Hal! I wouldn't do that!". I merely told the player "He was captured by his enemy, and who knows what was done to him before the suspended animation crown was placed on his head - deal with the situation." What happened next was a true comedy that even after all these years, I still chuckle over. The erstwhile Player Character #1 was beginning to beat up badly, player character #4. So the player running #4 started to hit back on player character #1 in self defense. Player #1, running player character #2 - started howling in anguish that his favorite player character #1 was about to be killed by a party member, so he JUMPED on player character #4's back in an effort to keep player #2 from killing his favorite player character! Player #2 took his walking cane and slammed it against the table yelling at the top of his lungs <Name redacted>! You CRETINOUS MORON!". So here I had the players fighting amongst themselves while they battled a Troll who had an Illusion Disguise on it to look like player character #1. They danced throughout that battle trying to render the troll unconscious, only to have the damage regenerate over and over and over. The Troll didn't have any weapons, and wasn't REALLY able to do MUCH harm to the armored player characters - and when they discovered that I had hit them with a Troll with Illusion Disguise on it, oh mannnnn - the looks on their faces!

30 years later, those faces are still a treasure to me. :)
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Old 04-29-2015, 11:32 PM   #26
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Default Re: Building permanent magical traps with GURPS Magic

Last and final nasty trap I'll share in this thread...

Once upon a time, player character #1 referenced in the previous thread, was in the process of being hunted by his arch enemy. Player character #1 had it all. A reputation as a fierce warrior/mage, married to a beautiful woman, and father to a precious daughter. He also had strength batteries that only he could use - otherwise anyone who tried to steal it would experience a magical attack capable of killing them. If however, the Strength Battery was given over freely - the person taking it could then use it.

So, the Hunter who finally captured Player character #1, kidnaps player character #1 and keeps him artificially wounded and weak so he can't cast spells or fight. When the player wouldn't permit the NPC to steal his prized strength battery, the Evil one went ahead and kidnapped Player Character #1's wife and daughter. Promising dire things would happen to the wife if PC#1 didn't give up his magic item, PC#1 still refused to give in. So, the evil one did those unmentionable things to the wife (using zombies I might add) to where the wife knew that the husband could have given in - but refused to. Making matters worse, then the Evil one got ready to harm the poor innocent little one, PC#1 finally relented and gave in to the Evil one's wishes. That is when the Evil one then cast a spell on the wife, had her draw her knife into the bowl with viscous fluid in it, and drag it across the daughter's skin - cutting into flesh. Within moments, the poor girl begin to suffer massive seizures and eventually gasped her last. Then the Mother drew the blade across her own skin and she too convulsed and expired. Angry as all heck, PC#1 swore he'd get revenge upon the evil one. Not content with his vileness - the Evil one clapped his hands as if casting a spell, and through an open doorway, replicas of the Wife and daughter came to the new dead wife and daughter, and began to dance obscenely over the corpses. With a howl of anger and frustration, believing that the dancing ones were illusions, he tried to disbelieve in the ugly creations of the evil one.

That is when the evil one said "My dear boy, try that little mental exercise on the ones lying on the floor." When the player did that, and the dead two ones on the floor disappeared, the Evil one said "What kind of monster do you think I am? Really!"

The moral of that story? Never take the straight obvious approach when you can. In a horror campaign? I once had a ghost possess a player character, then start up the car while he was possessed - and aim his vehicle towards unsuspecting children in broad daylight. Needless to say, when the player character wrested control of his character's body back from the ghost, he was unable to use the defense "The Ghost made me do it" when brought up on charges of reckless endangerment. Those players feared ghosts VERY much after that!

So - play games with them, and have FUN doing it. One GM took perverse pleasure in outsmarting me when he allowed my character to eavesdrop on a conversation of people I thought were going to attack my group of player characters. So, I took the news back to the players, and we planned a pre-emptive attack, little realizing that the poor guys had NO intentions of attacking our characters, and that I had been HAD. ;)
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Old 04-30-2015, 12:47 AM   #27
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Default Re: Building permanent magical traps with GURPS Magic

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Originally Posted by Grouchy Chris View Post
But the item still requires a user. Magic, p. 19: "Certain magic items are 'always on.' For the item to work, the user must wear or carry it in the usual manner."
That's allowed. The trap-layer is the user, he uses the item to zap the target area in the usual manner and the effect starts or is activated but paused. The Link turns it on and off, but it's still the same use, just like the Link on p.131 lets the one use of Continual Light last 168 non-consecutive hours. The Power enchantments allow it continue in perpetuity like any other Always-On item.
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Old 04-30-2015, 11:02 AM   #28
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Default Re: Building permanent magical traps with GURPS Magic

I've never been a fan of using GURPS Magic as-is for many reasons- (I'm sure you can find thread after thread after thread after thread of them), but as far as generating "magic traps" goes, you can do a number of things... 1) Create a Trap spell. It sounds stupid, but why not... Just use it like any other meta-spell or enchantment spell, pick an FP/ER value for it (both one-shot and permanent) , say it requires a few prerequisites like... Link, Avoid, Delay Spell, and you can cast spells into the "trap" to prime it and give it ammunition. Every time the trap spell is triggered, it releases the spell cast into it in the specified area.

If you want a "permanent" trap, require that you enchant the "trap" with power AND with the spell to be cast.

GURPS was made for custom work, and a Trap Spell seems completely and totally legit for what you are doing. Hope that works out for you =)

2) Handwaive it or GM-fiat it, nobody is going to cry later ;)

Last edited by Desthro; 04-30-2015 at 11:04 AM. Reason: forgot reason #2
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Old 04-30-2015, 08:25 PM   #29
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Default Re: Building permanent magical traps with GURPS Magic

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That's allowed. The trap-layer is the user, he uses the item to zap the target area in the usual manner and the effect starts or is activated but paused. The Link turns it on and off, but it's still the same use, just like the Link on p.131 lets the one use of Continual Light last 168 non-consecutive hours. The Power enchantments allow it continue in perpetuity like any other Always-On item.
It's not clear that that's not how an "always on" magic item works. P. 19 again: "These items don't let the wearer cast the spell -- they automatically cast the spell on the wearer at no energy cost." This suggests that "always on" items are not contemplated for anything other than what affects the user of the items. The FAQ, on the other hand, mentions both Flight and Deathtouch as spells that can be enchanted and Powered to reduce casting cost to zero, and Deathtouch is described as having the obvious interpretation as affecting targets other than the caster.

But however an always-on item that casts an area spell is to be interpreted, p. 19 of Magic makes clear that the effect ends when the user stops wearing or carrying the item. If the creator of the trap has to keep wearing the item in order for the trap to continue working, then it's not permanent in the same way an ordinary enchantment or a mechanical trap is.
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Old 05-02-2015, 04:43 AM   #30
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Default Re: Building permanent magical traps with GURPS Magic

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Originally Posted by Grouchy Chris View Post
But however an always-on item that casts an area spell is to be interpreted, p. 19 of Magic makes clear that the effect ends when the user stops wearing or carrying the item. If the creator of the trap has to keep wearing the item in order for the trap to continue working, then it's not permanent in the same way an ordinary enchantment or a mechanical trap is.
The addition of the Link spell effectively removes the requirement to keep wearing or carrying:

"Postpones the activation of one or
more linked spells cast in its area of
effect, until a certain thing happens in
the Link’s presence."

As I said before, the trap-layer can act as the user and initiate the first zap, which the effect of the Link holds until later and parcels it out under its description. The example under Link shows it time-shifting the Continual Light effect past when it would otherwise end, so it ought to time-shift a Create Fire effect past when it would otherwise end.
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