In the interest of not having overly long lulls in the blog while I sort stuff out behind the scenes, I'll post some reliable baseline info on my take on a SotC magic system for "Spirit of the Sword" (by the by, how does "Spirit of the Crown" grab you?).
First of all, be warned that some of the details here are still being worked out. But then again, that goes for just about everything on this blog.
After thinking about whether or not to cut Magic as a skill altogether, I've decided that yes, I'm going to go ahead and do that very thing -- but it can easily be re-inserted into the skill list, and I'll give guidelines for doing so, for those who prefer it. At any rate, all I'm going to go into for the time being is which skills are getting which types of magic, and why.
Artifice involves the creation of enchanted items, such as troll-slaying swords, amulets of power, and concealing cloaks. Artificers employ time-tested techniques in these endeavors, passed down from master to apprentice over the centuries, and only items of the finest manufacture can be imbued with magical power. Thus, Artifice uses the Crafting skill.
Magecraft is the direct manipulation of intangible magical forces to alter reality, such as flying or flinging destructive fireballs. Mages accomplish this through very specifically intoned incantations and highly refined gestures that aid the mind's focus. These performative aspects put Magecraft under the Art skill.
Those who practice Necromancy possess knowledge of the secret underpinnings of life and death, though applying that knowledge often proves... unpredictable. They seek out these occult mysteries in books, scrolls, and tablets written in an ancient, unknown hand. Few now can recognize the forgotten tongue in which they're written, let alone decipher them. However, unlike Magecraft, Necromancy requires more than the right word at the right time. The practitioner must establish a certain connection with the world beyond, with the living and with the dead. And there are some who whisper that the true secrets of Nnecromancy aren't learned, but felt, as if imparted by an external agency. This is why Necromancy relies on Empathy.
Summoning is the act of calling creatures into existence through a combination of arcane knowledge and sheer force of will. Using the same principles, the summoner can also make solid objects, such as a wall or a sword, appear out of thin air, if only temporarily. Such efforts are taxing on the psyche, however. Summoned creatures must be dominated and bent to the summoner's will, a struggle which relies on Resolve.
Alchemy is a strange case, and its associated skill is still pending. Arguments can be made for it to fall under Crafting, Lore, or whatever Medicine gets renamed to (still probably Physick). Alchemists create potions, elixirs, powders, and the like -- magical chemical compounds concocted from established recipes (Lore) requiring an intimate knowledge of the elements and bodily humours (Physick) and so precise as to preclude even the smallest error in the formulation process (Crafting). I'm leaning towards Physick, because I like the idea of making Alchemy as scientific as possible. That, and Lore and Crafting already have their own magic, and I'm trying to avoid doubling up. (Edit: Oops -- Lore doesn't have its own magic anymore.) I'm intersted in hearing any feedback anyone may have on the matter.
Be that as it may, Alchemy, Artifice, and Magecraft work much the same way as SotC's Gadgets or Artifacts. The product of each, whether a potion, an item, or a spell, is composed of a number of improvements, or effects. Generally speaking, Alchemy and Magecraft conform to pre-defined packages of effects that characters learn. Invention of new spells is a snap, although it requires some guidelines to keep the different forms of magic feeling different. Artifice more or less follows SotC's rules for making and improving things, only the things come out enchanted when you're done with them. Necromancy and Summoning, on the other hand, have a lot in common with the minion and companion rules (especially Summoning), although each does things outside that scope as well, such as a life-draining necromantic touch or a summoned object.
There's more to say about magic, even at this early stage, but I have a football game to get to, apparently.