GM defenses against invisibility and other spells

[Michael Lewis]

I am a newbe GM and am running a Yirth campaign. One of my PC's is a mage that has the invisibility spell. Since this is our 1st time using GURPS, I did not realize how powerful that spell is likely going to be. Does anyone have some suggestions against such spells as those? Should I have outlawed such spells before hand?
Any other suggestions will be appricated.

Michael

[laserdog]

The rules allow foes to make hearing-2 checks to locate invisible foes, and get defenses against their attacks.

Also, anything with discriminatory smell probably wouldn't have too hard a time figuring out where he is either.

So I recommend sic'ing wolves on him. =)

Or, there are always beings who naturally see invis?

[sir_pudding]

Some nerfs:

• Make sure you charge FP whenever possible (encumbrance, extra effort, starvation, lack of sleep). At 5 energy Invisiblity is expensive, with no FP he can't cast it.
• Magical Countermeasures: See Invisible, Dispel Magic, and Sound Vision
• Mundane Countermeasures: Flour, ect.
• Enviromental Countermeasures: Rain, Fog, Smoke, Water and No Mana Zones
• In darkness, the character is equalized with the foe.
• Foes with Blindfighting.

[arnej]

I'll second the attention to Fatigue. If you can construct a scenario where he
has to keep Invis up for an extended period of time, it will prove much less
useful. So, for stealth-based Invis use, make the objective something he has
to search for.

Or does he just use it in combat? If so, make sure that you keep track of how
long it takes to cast (pretty sure it's not 1 sec.) Have the baddies whack him
while he's doing the magical happy dance, and he'll be rolling vs a hefty penalty
when he finishes...

Arne

[sir_pudding]

Originally Posted by arnej

Or does he just use it in combat? If so, make sure that you keep track of how
long it takes to cast (pretty sure it's not 1 sec.)

3 seconds.

[transmetahuman]

Originally Posted by sir_pudding

Some nerfs:

• Mundane Countermeasures: Flour, ect.
• Enviromental Countermeasures: Rain, Fog, Smoke, Water and No Mana Zones

• Hearing should be significant. Ask a friend to walk around on a noncarpetted floor or outdoors, and close your eyes. I bet you know where he is to within a yard, if he's nearby. Now ask him to swing a heavy sword around, or just exert himself aerobically... hear those grunts and heavy breaths? Don't forget to have foes make those hearing rolls (but also remember to give minuses for background noise, like everyone else running around exerting themselves)..
• Mud, soft earth, sand, grass and other ground foliage move when you step on them. So do a lot of carpets. I'm not sure how to run this in a game, and I'd give minuses to the roll to notice if the person isn't on the alert for an invisible foe, but there are times when I've wondered if straight invisibility would be anywhere near the level of undetectability that fiction makes it out to be.

Don't take it too far, though, and make the mage feel cheated out of his points.

[Kale]

Since the world has fairly open magic, it's likely that defenses against such a spell would be quite common. Even a non-magic-user guard might have been taught rudimentary tactics to use against a foe using this spell. Throwing around sand or dust, blocking a narrow corridor, and the ever popular lighting the area on fire tactics come to mind. A little lamp oil can really ruin your day.

[PK]

Everything proposed on this thread has been very appropriate and believable, so I heartily endorse the suggestions here. However, I'd like to throw in a crucial tangent: Use these countermeasures, but don't overuse them.

The player put points into Invisibility and all of its prerequisites for a reason -- he expects (and rightfully so) that he'll be able to use it to gain an advantage in many situations. So make sure that you don't make it completely useless. Foes who are alert (guards, anyone in combat, etc.) should always get the Hearing-2 roll, but otherwise effective countermeasures should only come up once in a while, or when the plot demands it.

If it just happens to rain or the foe has a bag of flour in his belt or someone knows See Invisible or the ground is full of crackling leaves every time the player wants to use Invisibility, he'll rightly want to know why you let him waste the points on it.

[DrTemp]

Originally Posted by sir_pudding

[...]
Magical Countermeasures: See Invisible, Dispel Magic, and Sound Vision
[...]

It should be noted that See Invisible won't help all that much, since few guardmages will be able to have it active all the time. NPC's must pay FP costs for spells, too.

[Michael Lewis]

Thanks everyone so much for the input. It helped me a lot.