Its been a while since i've posted so i thought i start again with a rules query.
If my magus casts a spell that causes +15 fire damage (CrIg of course) and has duration diameter, does this mean the spell inflicts this damage once? Every round? Every minute?
Consider a hypothetical ReHe spell that picks up a spear and stabs someone, with duration concentration i could use it to attack each round. If i made it a CrHe(Re) spell i could create a magic spear and attack each round. If i could do it with a spear, should not the fire burn each turn too?
A perdo corpus spell with a duration has been stated to make the wound endure that time length, i.e. no healing. But could a spell be created that slowly flayed a man (for instance) inflicting multiple light wounds over time, during concentration for instance.
Have any of you come across this in game and if so, how did you solve it?
By the raw, CrIg creates a fire at a given location (CrIg at voice range is creating a fire anywhere at voice range, CrIg at touch range is creating a fire where you can touch...).
A momentary CrIg spell creates such a fire, for a moment. Longer durations make the spell last longer, so you may take damage each round for it.
BUT since the target is the fire, and you create it at a given place, it'd do this damage only where it resides, and not "follow" a target. This may produce strange effects with the "free" visuals of, say, a PoF, but a mom duration pilum would target the same place for 20 rounds, not the same person. So, if the victim didn't move, it'd get burned each round, but, well, who would stay in a bonfire?
You could, of course, find ways over this, by adding a Rego requisite to the spell. As you note with your spear, maybe this would only work with concentration duration, though. But I'd certainly accept a Cr(Re)Ig with concentration duration allowing you to target anyone for +15 damage as long as you're concentrating.
There's mastery and multiple casting for this, so I'd say no. There's a RAW spell that does something similar with fatigue at concentration duration (Grip of the Chocking Hand), but it seems more like one of those sad remains of previous editions than anything else. Note, though, that even with this, the spell's description gives a rationnale as to why this cumulates.
Anyway, due to how wounds work in 5th ed, I'd strongly advise against this, or you'll quickly see medium wounds stack up: A Level 25 voice/mom, same as inflict a Heavy wound, would create an additionnal -3 penalty per round without you doing nothing instead of -5 once. Worse, you could cast such a spell each round... you get the idea.
Making this king of thing possible only with concentration duration would make things better and more balanced, though.
Check out Coat of flame on page 140; +5 damage every round and it does have a rego requisite. Yet the text says "The rego requisite ensures that the fire does not spread" implying that if the caster didn't care about spreading the fire then it wouldn't be necessary.
Well, it is a Personnal range spell. Moreso, the guideline includes an extra magnitude for "covering an item", which, IMO, includes it "sticks" to the covered item.
For a counter exemple, why does "Circle of Encompassing Flame" stick to the place it was created? Simply shrinking/expanding it requires a rego requisite AND concentration, we're not even talking of moving it around to follow a moving target.
Of course, you could very well rule out that continuing spells at greater ranges on someone are possible without any limitation or additionnal requisite, but I think that's not justified, and is opening a little pandora's box (One more magnitude, and instead of a single PoF per round, you're doing cumulative + 15 damage per round without any additionnal difficulty).
It's range voice not personal, but it does have the higher guideline for unnatural shape.
nice counter example. To create an argument against this example, the circle is cast upon the ground and if you moved the ground it would seem that the circle of flame should move with it even if it were a spell without a rego requisite.
Wise idea or not, coat of flame is a range voice spell.