You only need to make eye contact at time of casting, much as you don't need to keep hold of the target during a Touch range spell.
Neither, by the RAW. For the PeIg spell in question, the target immediately suffers the loss of 2 fatigue levels and then cannot regain them whilst the spell persists. The RAW doesn't support incremental effects like slow loss of fatigue or health, or the gradual dwindling of Might.
Taking this basic assumption for a fact (is it correct?): If you cast an Eye spell with Sun duration, you need to make eye contact when casting, but not for the entire duration.
I would say that you don't need to maintain eye contact during a Concentration spell either.
You could rule that to make changes in the effect, you do need to regain eye contact. (this is not important in your chill spell, but could be vital with a fly spell for instance)
As to why, because that's the way they're phrased. A PeTe spell to create a hole doesn't allow you to make the hole bigger by wandering around for the duration, it merely means that any dirt chucked into the hole also vanishes, preventing it being filled. The spells destroy specific things - in this case, exactly enough of his body heat to cost 2 fatigue levels.
You can arguably get damage over time by creating fire with a duration, since although a finite quantitiy of fire is created, the damage it does is a function of its existence.
I don't believe so. Being able even just to cancel a spell before the duration has expired requires a virtue (Harnessed Magic) and that requires concentration equivalent to spell casting to do so. You might be able to invent a spell which allows that, but I think I'd require additional magnitudes and successful experimentation in the lab to do so.
There is an example spell in the book, under PeCo, that slowly chokes the target. It uses the base for inflicting 1 fatigue level and uses concentration duration to inflict 1 extra fatigue each round. (It specifically states that you cannot kill a person in this fashion, by the way)
This is true, though looking at the spell's description is looks like a legacy spell - Grip of the Choking Hand actually chokes the target rather than just inflicting a fatigue level - and should probably be ReCo(Pe)or PeCo(Re).
I think that ExarKun's spel could work, but not using the standard guidelines. As a result of experimentation, however, it'd be rather cool. Pun not intended.
His example is very reasonable. You create a chill that costs 1 fatigue level on the target and by concentrating, you can hold the chill there that he continues to take damage. (get him cold and keep him cold) as opposed to just a brief chill. This is a matter of destroying the heat on him and keep destroying any new heat on him.
The key is the following:
You cast the spell, it will have its effect every round as long as you maintain concentration. You can break concentration to end spell and effect and need to recast it or you can let it keep having the effect.
The option to have it have the effect and then each round you chose whether the effect occurs or not is one of those things that is not an option.
I guess you could add +1 magnitude for Rego Requisite for a chilling wave that moves about the room and that you can move over the target for 2 fatigue levels.
Keep in mind the concentration rolls for talking (EF 15 to maintain spell).
I will say though that I would not allow the 2 fatigue levels a round, but only 1. If it is so cold that you would be doing two per round with PeIg, you are in the territory of frostbite and damage, not fatigue. I would say on art that could do 2 fatigue would be PeCo since you are draining the body directly.
How would you handle a Wound That Weeps with Diameter duration? Does the wound increase in size? To a certain extent, I can see the logic for a spell which "creates" cold, but in this case it destroys warmth, and once that warmth is gone, it won't make the target any colder. The fact that the cold causes the loss of a Fatigue level is a mechanical consequences of being that cold, not an ongoing effect.
Wound that weeps: you cannot stop the bleeding for Diameter duration
Colds spell: you cannot warm him up for Diameter duration. After a while he loses a further fatigue level,and after a while a third.... The further loses might not be linear at all or equal for all targets. Make the descriptive scene make up the effect
This would be my interpretation. Whether or not that leads to loss of additional wounds due to bloodloss is, however, up for debate. The bleeding wound is, after all, a cosmetic effect on top of the guideline.
Wound that weeps with diameter would do a light wound every round until duration expires. This means they slowly bleed out. 20 light wounds worth should be deadly. The 6th light wound basically cripples the person (-6 to activities.).
Not up for debate. if you want a "real!" wound, increase the effect pof the spell by a magnitude. Then it will cause a liught wound or a second level of fatigue loss. It would not be cosmetic in that case
And that, frankly, is obscenely powerful. It also emulates a recasting of the spell each round rather than sustaining it.
I agree, really. I'd say that the causing of slow degradation aren't really covered by the guidelines, save perhaps as "causing a disease", in which case it's a little odd that it's easier to make flesh part than stop working properly. I imagine that, abstract as Ars Magica's damage system is, the light wound's season long penalties incorporate the effect of the bloodloss. And that's why the sustained PeIg spell seems off to me.
Remember the Central Rule (p 111) - don't let the rules break the game.
There are several spells that place "additional limits" on their effect - the target cannot be killed by choking, the target take no more damage after dropping unconscious, etc etc. Balance the spell effect with its level.
(And, unfortunately, it is true thatt here are many spells that are "legacy", left over from previous editions, that are terrible examples for the current rules. If they don't fit, don't try to force them.)
I'm not convinced that adding "Concentration" to a spell that causes a wound will cause more and more wounds. Let's take the reverse, a Creo Corpus spell. Does that heal more and more wounds, or does it merely keep that one wound healed for duration?
We were discussing something similar in a different thread, and the interpretation of "One spell, one wound" seems reasonable in most cases. It avoids the unbalancing effect of a dozen Light Wounds that some cheap effects might otherwise cause.
That is the widely accepted interpretation. It generally makes far more sense and has a better "feel" than alternatives. (Tho' mixing "common sense" and magic rules often a big mistake!)
This usually requires the addition of one additional Magnitude for "complexity" - the ability to turn a spell on or off (or otherwise change the defined effect) at will is not part of a basic effect from the Guidelines. (Some enchanted devices may allow this tho', depending on their design.)
And, usually, to change a spell the target must still be within the original spell range. A Touch spell with 1 level of added complexity does not allow changes at Range: Arcane after the target leaves your knowledge.
Some spells (especially direct damage) obviously do additional damage if given longer "durations". But a single magical effect is not multiplied upon a target with one single casting of a spell. The duration can guarantee the effect lasts (as in Sleep spells, or against counter-spells), but "one spell, one effect" seems to be in keeping with The Central Rule for most spells.