What about each added magnitude for complexity equating to a +3 on the Finesse roll? As is, a vanilla Conjure the Mystic Tower would then have +9 built in.
For someone in the magical construction "business", a good investment might be a multi use item based around some of the A&A rules. A stone façade is a one year project, so a R: Touch D: Mom T: Part +2 Size = level 15 ReTe spell/effect will do a little over 2500 sq. feet of surface a little over 1 foot thick (or about 3 casts to cover a Mystic Tower) with a -12 modifier. Dropping the spell/effect down a point of size should qualify as a stone relief (a one season project for -9), but need more casts. A bronze mason's chisel with some copper and marble inlay gives S/M relevant bonuses of +3 Terram, +2 shape stone, +4 deftness and +3 beauty to work with and can be opened for 10 pawns of vis. An unGifted but skilled mason with some Finesse training/practice could then do a lot of the aesthetics work on a section by section basis.
Remember what Covenants said about concentric castles. The local powers cannot ignore a construction of this size; even envisioned as a city, conjuring this out of nowhere will appear as a threat to every lord up to and including the king.
(Contrariwise, if this is done on the Magicians' Isle, then it will simply be a further demonstration of the might of the magus-lords.)
Having one more breakfast coffee, I make a simple computation:
(1) Comparing the draught horses between inner wall and citadel with a tower on the outer wall to the right, which by laws of central perspective should be in scale with the horses: three horses head to croup span the diameter of the outer wall tower.
(2) Comparing the diameter of an outer wall tower with the wall segment between two such towers at the front of the drawing: five tower diameters roughly make up the length of the wall between two towers.
(3) Counting the wall segments - yes, this is walking over gates and irregularities in the outer wall, but still:
the outer wall has roughly the length of twelve times the above wall segment, towers included.
So the circumference of the outer wall is roughly 12x(5+1)x3 = 216 draught horse lengths. Something around 500 m.
The problem is that there seems to be a required level of Finesse roll for the spells to work at all, rather than just rolling the Finesse and interpreting the result. The Core book didn't have this problem, Covenants introduced it for Rego craft magic and HoH:S extended it to Creo magic, but doesn't quite make it clear if it's a requirement for success of a list of guidelines for results.
For example, a best case CtMT is (as above) is Finesse 24 (15+9), but if you roll a Finesse 18, do you get a tower built by semi-skilled artists (9+9), or just a pile of junk? It's pretty obvious that these rules are extremely difficult any decently sized magical conjuration, as rolling 18-24 on a Finesse check is prohibitively difficult. Yet the game seems to assume that CtMT is a default, go-to spell for covenant building.
Personally, I sort of think the +3 magnitudes for elaborate design is a 'potential' for the spell rather than a requirement. Want a fairly plain tower? Cast CtMT with lower Finesse expectations and you're done. Cast a similar, 'dumbed down' version of CtMT without all the elaboration and your Finesse roll of 36 still gets you a plain tower. An average roll for a magus skilled* in Finesse will be something in the order of 12-15 (Finesse 5-6, +2-3 Int, Roll 5-6) and that's IMO where the target for getting something decent out of Creo magic should be.
*'Skilled' in this case assumes rough equivalency to a journeyman or young master of a craft; Ability 5-6.
Last time this came up I argued for some Rituals to be "planned and designed" to the point where the Finesse roll was moot. In play we added a story segment which was the NPC caster spending several weeks in preparation, to design each aspect of the tower. For rituals such as CtMT I think that is far better than a finesse check.
For non-rituals, then sure roll Finesse. Perhaps the guide should be a +1 to the Finesse check for each day the caster spends working on how the spell will be cast. You could even use the pyramid scale from XP if you wished to require a massive amount of days to be required for the bonus. It certainly will stop it being a cheap work around. Time is life to a Wizard.
This makes a lot of sense and could remove flexibility from the spell. Cast CtMT and you get the same tower every time, as its template is built into the spell (and, by extraction, enters the Realm of Forms after the first one is created). I guess it depends if each casting is prepared or the planning goes into the invention of the spell; I can see either argument. Most creo spells are pretty specific in defining what they create anyways. In this case, though, consulting a professional architect to get designs is pretty much a must; this sort of replaces Finesse rolls with Profession or Craft rolls (but you can cheat and hire really good craftsmen as consultants).
My understanding is that if you fail the finesse roll you still get what you were conjuring, but with no frills. So for CTMT it would be a perfectly circular grey building with rooms all the standard size and standard windows etc... there is a lot of detail work that normally goes into making a tower that the magus failed to effectively specify and so they got a plain old vanilla tower.
I like the idea of preparing a ritual for days before casting to avoid rolling for Finesse.
Since time is the most valuable currency, I would go with the rule that the final quality is equal to the number of days spent in preparation.
During this time, the magus is drawing and memorising the final results he wants to achieve, but he is also calculating horoscope, using gold number and other tools to make sure that he will get the results he want.
I will also go with an additional rule: Weirdness (or magical air): for each 3 points of quality, the objet gets 1 weirdness point.
Weirdness score is an attribute which describe how unnatural the objet looks for a mundane onlooker - the gift protect from this effect. It is the equivalent of the gift, or the blatant gift for magic-made item. It manifests into strange shadows, feeling of being haunted, feeling that sculpted face are moving and so on.
A gifted mage, or a mage willing to spent days and days can achieve high quality artwork, except that it will always carry a strange aura, that mages are oblivious. And a magically-made item will never be the same as a man-made item.
Under aiming for casting indirect spells, for every magnitude the spell is above the size of the object being affected gives +6 to the aiming roll, which is based on finesse. I could easily see generalizing this to craft magic use of finesse as well. Also note the familiarity bonuses from 'encounter on a daily basis' are +3, ad most magi will encounter a tower or town on a daily basis.
On the other hand a finesse failure could well mean you forgot to make bricks in the walls and made them smooth, for example, so they don't look right.
This isn't quite accurate. I presume you are referencing this line:
Note the Size of the Individual is what's key here not the magnitude, and if you increase the Size (and thus the magnitude of the spell) you make it easier to hit, because your medium for attack is larger. Throwing a bounder the size of a car gets a better aiming bonus than a sling stone, but a worse one than the size of a house (serf's parma, I didn't do the math to see that the volumes required an increase in size, I'm just presuming that the house requires an additional size increase over the one used for the car).
That being said, there is precedence with some canonical spells having magnitude increases for complexity or elaborate design. I tend to think these things are fine, but need to be listed as part of the spell's design.
I do, too. I also like the idea of spending a lot of time to mitigate botch risk, which was part of my thought behind Rethinking Ritual Magic thread a while back. I think it makes some sense that a magus conjuring a Mystic Tower would spend a season designing it and ultimately casting it, making prudent choices about the design, perhaps even having scale models of it, which would be aids in the casting, and potentially all of the issues worked out. Mind you, I was talking about the time frame of a season. But there was enough push-back against the idea that I ultimately dropped discussing it...
Yes, and I pointed that out. The core book doesn't say 'you must roll this well' to use Creo magic with Finesse. It just implies that the quality of the creation is proportionate to the roll.
HoH:S, however, says that Creo magics have the same targets as Rego magics for Finesse rolls.
"When creating artificial objects, the same level of Finesse is required as when using Rego to make them from raw materials." HoH: Societas pg 60.
Also, the sidebar on pg 61 is "Ease Factors for Creating and Crafting Objects". An Ease Factor is a target for a roll. What it doesn't say is what happens if you miss the target - that's clearly defined for Rego craft magic (you make a mess), but not for Creo conjurations. The implication seems to be that if you miss the Creo target you get a mess, as with Rego, but it's not clear.