Alright, I got into an argument with one of my players about his armor. He has a character with 5 lore and his Thaumaturgy bonus is to strength. He says that somewhere in the book Your Story he found that he could half his rating (6) and make his coat into armor 3. That we have found, but then he says that he can make it permanent by halving the total again, for an armor 1 that is always on. We cannot find that part, and for the time being I have allowed it, but I was wondering if someone could point me to the page that this is found on, or tell me if this is just bull.
[RPG] Permanent Enchanted Items in Dresden Files
It's easy to miss, but it says on p. 251 (just before the example) that the Discipline roll used to cast the evocation counts as the attack roll. The amount of stress inflicted by a successful attack is equal to
(attack roll - defense roll) + weapon rating. In the example, the relevant numbers are:
- Attack roll: 8
- Defense roll: 4
- Weapon rating: 8
attack 8 - defense 4 for success and stress of
4. Since this attack was made with a weapon, now add the weapon's rating:
stress 4 + weapon 8 for a total of 12 (less one for Inhuman Toughness).
The math isn't the same at all in the case of losing the opposed roll. If the attack roll doesn't beat the defense roll, then the weapon rating is never factored in and the equivalence breaks down.
So it's not quite "shifts you put in plus your Discipline roll" minus defense, it's the mathematically-equivalent (but procedurally and conceptually different) "attack effect plus weapon rating". If it's easier to remember the first way then that's fine, if you win the opposed attack/defense roll. If you don't win the contest, then thinking of it as "shifts plus Discipline" will just cause confusion.
Here's an example of how the math works when the attack loses the contest:
Harry is fighting one of the Vampire's minions now. He fires off the same evocation that took out the minion's master, putting in 4 shifts—he doesn't want to deal with backlash or fallout just to deal with some poor thrall.
Harry's evocation is a weapon:4 and his Discipline is Great (+4) so he only needs to roll 0 or better on the dice. He rolls 1, so his total Discipline roll is 5. That's enough to control the evocation, and doubles as his attack roll against the minion.
Against all likelihood the minion rolls exceptionally well, getting a +6! Harry's loses the opposed roll and his attack fails, even though he cast the spell successfully.
Now, the numbers look like this:
Discipline roll: 5 Shifts put into the spell: 4 Attack roll: 5 Defense roll: 6 Weapon rating: 4
If we use your math, then the attack is
Discipline roll + shifts in spell:
5 + 4 for an attack of 9. Less defense of 6, that would deal 3 stress to the minion.
However, that's not how attacks are resolved! Using the actual math, the attack is
(attack roll - defense roll):
5 - 6 which is -1, and since rolls never generate negative shifts (p. 17), the attack is just considered to have failed. The minion won the opposed roll and the weapon rating becomes irrelevant—weapon rating is only added to the shifts generated by a successful attack. The minion suffers no stress, and now Harry is in a bit of trouble…
First a point of clarification: typical Thaumaturgic focus items don't give you a choice between bonuses to Conviction and Discipline, they give a choice between bonuses to Lore or Discipline. (Conviction and Discipline bonuses are the options for evocations, not thaumaturgical rituals.) And to clarify further, the bonus is to either Lore or Discipline, not Lore and Discipline as you have it written in the question.
That said, when creating a thaumaturgic focus item for crafting rituals, you can choose either a frequency, or strength bonus (see YS p. 280, top of the second column) instead of a Lore or Discipline bonus. However, notice that such a focus item would only be useful for creating enchanted items since strength and frequency are irrelevant to the creation of focus items (and the book even says that you can't use focus items to make other focus items).
Finally, it's worth noting that taking Ritual with a specialisation in crafting won't let you create more focus items and enchanted items than you have focus item slots and enchanted item slots:
Wizard characters get a number of “slots” for different kinds of items, under the assumption that there is a practical maximum of items that a wizard can make and maintain at one time. That number rises via character advancement (and the purchase of the Refinement ability—see page 182), allowing the wizard to either possess more items or create stronger ones. —YS p. 278
To get more slots to fill with your creations, take Refinement during character advancement.
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There was apparently a change in the enchanted items rules between the printing of the books and the early access PDFs that were sent out. The original always-on rule appears in the early access PDF, but not in the printed Your Story rulebook for Dresden Files RPG.
So all of the below from my original answer may be completely ignored if you so choose.
From those PDFs, on page 279 of Your Story -
Combining this with the block effect used as armor rule on page 252 that you reference, that would make it a 6 point block spell, halved to be converted to an Armor:3 usable spell effect, and halved again to make an Armor:1 always-on.
This is basically a copy of Harry Dresden's leather coat, which is actually an example listed on page 303.
In the printed official rulebook, there are several ways to increase the number of uses per session for any individual item - decreasing it's strength by one provides one additional use, using another enchanted item slot provides two additional uses, and the effect can always be triggered again by taking one point of mental stress. However, the always-on effect rule has been removed.
The section does note that defensive items simply consume a use at time of defense rather than requiring an action to activate, so your player may well be able to work with that once he figures out how to invest in the item.
As well, the Duster example has been changed to an Armor:2 usable effect example, with additional uses (3/session) provided by using an additional item slot.