Illusory spells of all sorts (i.e., those which are Simple, Complex, or Perfect Illusions) can be Disbelieved. The metaphysical explanation for this is that their astral structures are fragile and more easily disrupted than normal spells. Any Adept can attempt to disbelieve a spell by concentration and effort: this takes a second of concentration, costs a Strain point and requires a roll vs. Will, with a penalty equal to the circle of the spell.
*Anybody* gets a free disbelief test if they succeed on any test interacting with the illusion by five more than the disbelief penalty. So, for example, if a Thief succeeds on a Lockpicking roll vs. an Illusory Magelock by more than 7 (Magelock is a second-circle spell), the spell dissipates.
The above is the mechanic we're using as of 29 October 2002. The notes and argument which led to it are below.
My only issue at this point is that I don't have any real sense of what 'circle' most illusion spells are. Many of the repeatable threads logically give more opportunities for people to disbelieve (extra targets, longer duration, bigger area) but some might not (like extra effect). Threads, of course, don't change the Circle of the underlying spell.
Adepts can get skills in the high 20s. An illusionist picks up a 3rd circle illusion spell and False Sight at 3rd circle, and cranks false sight.
She can reasonably expect to get a margin of 10 on her false sight contest, meaning that the opponent has to succeed by 18 on a willpower test (hahaha) or 26 on their skill check, taking us back to 'crits only.'
Mundanes just sense on crits (so you can expect an illusion to deal with 25ish interaction before you worry about it vanishing),
and Adept Disbelief can be put into the same category with some work, which is an indication that this system is broken.
Part of this should include damage to illusions no longer causing skew (or no longer *only* causing skew). Mirages should react like the mundane objects they simulate.
The original rules are at http://www.evenmere.org/~bts/EarthdawnCD/EDRULES/11_SpellMagic/SpellMagic6.html
I don't think disbelief should be accumulatable: in particular, I don't want two effects:
* I don't want a party to have a guaranteed time by which they can disbelieve an Illusion.
* I don't want disbelief to be laughably difficult. I think the current mechanic is broken, in that disbelief is basically impossible.
The original rules got this effect across pretty well. I'm editing comments in place above, Jesse, just to try keeping ideas localized within the page. --bts
Let's look at how Will-SpellCircle does for Disbelief, and Skill-(5+SpellCircle) for Sensing:
* A first-circle illusion spell cast by a non-illusionist is gone in seconds of disbelief with adepts, but survives for a while against mundane interaction.
* A third-circle illusion spell requires three or four disbelief attempts before it falls, and expert mundanes can sense it without a crit, with repeated interaction.
* A fifth circle illusion spell is sensed by mundanes only on crits, though skilled adepts (high 20s, as mentioned above) will still often sense it.
* A third-circle Illusion backed by seven ranks of False Sight (high, but not unreasonable in this party) is disbelieved on a Will-10 roll and Sensed on a success by 18 or more... indeed, effectively impossible. But it's an illusion by a professional illusionist who's concentrating on preventing it from being sensed (read the FalseSight mechanic again).
* At the very high end of the scale, a ninth-Circle illusion backed by 15 ranks of FalseSight requires a Will-26 roll to disbelieve and a success by 31 to sense. Note that several current party members roll that well about once per run *now*.
I'm not worried about this creating overpowering illusionists (especially since we already have some). If anything, I'm worried about it making Illusion useless and causing Illusionists to always cast their spells Real.
When illusion mastery is added in, it seems like illusionists suddenly gain the ability to do 12d of damage to anyone at 4th circle. (Will-10 to disbelieve rolls aren't likely to work well for most anyone) Perhaps Perception could help or something? I'm sure that wizards were supposed to gain the ability to heavily zot, but I wouldn't have expected illusionists to be the best at it. -trhyne
What's Illusion Mastery? Do you mean SpellMaster, the magician's parallel to WeaponMaster? Or do you mean FalseSight? And, um, go read the node on how to get an illusion [Disbelieved]. 12d real damage at range is going to involve... innovations from most Illusionists. (Ephemeral Bolt does 4d, so could be made to do 12d with three Reality threads and two Extra Damage threads, for a total size of 6, and a risk of Talent Crisis. On the other hand, a fourth circle Illusionist spell which sucked all the karma out of somebody and gave it to the Illusionist doesn't sound entirely off-base. That sounds nicely balanced with the similar-Circle Elementalist spell which causes all natural objects (plants, animals, rocks, rivers...) to lash out at you and try to kill you for the next year and a day; the Nethermantic spell which summons your Ghost through time from the future to ask it questions; the Wizard spell which binds a target to spend the rest of his life working on an impossible task... and, indeed, the effects available to an Archer at Fourth Circle.
Yes, a character who is under the effect of FalseSight will have difficulty removing illusions... though if you read the mechanic, you'd notice it must be used once for each (person,illusion) pair. Less than comforting in the case of Ephemeral Bolt, I know. But to get a Will-10 disbelief check for Ephemeral bolt, the Illusionist needs 8 ranks of FalseSight... hardly normal for a Fourth Circle Illusionist. --bts
Pumping single tallents is something that players do, especially in this game, especially when there's long periods without good opportunities to circle up. And pumping a tallent that makes all your spells more effective seems imminently reasonable choice for a player, the moment they get their hands on that tallent...and trust me, its always useful, so you're almost always able to meditate it up.
On the other hand, it makes sense to me at least for sensing tests against damage to be rolled againt the amount of damage dealt...so if you're taking 42 points of damage from a 12d ephemeral bolt, you're even likely to succeed by 30ish, and shrug the effect right off. It might even be the case that you roll against your accumulated illusionary damage. (since the illusion is simulating the effects of more and more severe damage, stacking more and more damage effects is bound to get tricky).
On epossible way to get around making suber-powered illusions Real with an extra thread or 2 is for the illusionist to need to add reality to each level of effect--so if oyu have a 4d ephemeral bolt and weave 2 extra effect threads and enough threads to make the base damage real, you've got
4d real damage and 8d illusionary damage...a rather neat effect, actually.
One problem that exists with high ranks in tallents is that you're often adding two roughly equal number together for your total skill--so anything that's tested against just a stat is laughably hard when it's just being reasonable for a stat+tallent. I know this is a problem for many rpg systems, though not nearly so much in general GURPS. Perhaps there's a good fix hiding someplace...Avoid Blow is good for physical attacks, Resist Taunt is probably as good against social attacks, nad I expect Steel Resolve to be a reasonable equivalent against mental attacks (Mind over Magic also seems to work well against spells, but several levels of Extra Penetration can probably overwhelm just about anything.)
I'm beginning ot think that Extra Effect threads may be a little broken, but they do have this nice interesting effect--adding the base effectiveness to a spell increases its cost by 1, and so takes one more action to unskew, which seems about on par with archers (who have no base cost to unskew, but whose missiles don't add together before armor).
--zebediah
It doesn't make all your spells more effective: it has to be used on each (spell,observer) pair separately. Damage for sensing tests doesn't work because damage and skills are on entirely different scales. There's stuff out there which deals 6d*200 damage, and the party's very likely to encounter it. That's why damage is sensed on the HT roll. I do like the idea of reality being needed for each level of effect quite a bit.
That's an interesting analysis of Extra Effect. I'm going to have to think about it a lot more before I say anything substantive. See BriansLatestMechanicsRant.
--bts