Spellcraft represents the knowledge of spells, specifically, how they work, and what they can do. It’s basically Knowledge: Spell Engineering.
What can you do with this skill?
This is the skill used to learn spells (if you’re a member of a class that does that sort of thing), identify spells, identify magic items, decipher scrolls, and other related tasks. Which brings up the question: what the hell is Knowledge (arcana) for, then? It’s a good question, too, given that Spellcraft seems to be the much more immediately useful of the two skills. There’s a good argument that the two skills could be merged; I can agree with that, save that this new merged skill would be far and away the most valuable skill in the game (save Perception). But I think the problem here is a legacy one; the problem is that the boundaries aren’t clear, and they should be. So what we have are two choices; we can merge the two skills, or we can apply some logic and rewrite them both.
Or we can take the third option, and dump Spellcraft as a separate skill altogether. Do you know of any players of Wizards, Alchemists, or Magi who don’t max out this skill? Neither do I; that would be committing career suicide. Classes that rely on Spellcraft to perform their basic functions strive to pump it up into the stratosphere, and with good reason. Who wants to wait one level to learn a new spell off of a scroll after failing the roll? It’s a skill tax for these classes; other classes can more or less completely ignore it, if they want to. Sorcerers, they can take it or leave it; skill points are tight for Sorcerers, and there are better choices. Even if a Sorcerer wants to identify magic items there are better ways than maximizing Spellcraft. Clerics and Druids, ditto. Bards have skill points aplenty, but they also have such an awesome selection of class skills that they can go whatever way they want, and they can always wait until they have Jack of all Trades if they want. Other classes have the same issue; Spellcraft may just not be worth it. Counterspelling? Bah, who does that, and why wouldn’t they just use Dispel Magic to deal with the issue? Building a dedicated counterspeller works better with Improved Counterspell and Dispel Magic. Of course, there’s always the cool concept fighter who doesn’t cast spells but maxes out Spellcraft so that she knows how to deal with the spells that are coming.
Yeah, I’ve never seen her either. And once you stop laughing we can move on.
So here I’ll present two options. One, my preferred option, just folds all of Spellcraft’s functions into Knowledge: Arcana. Bam! That was easy.
Here’s the other: Spellcraft is for spells, period. No identifying magic items (use K: Arcana). Take anything referring to spells specifically in K: Arcana and move it to Spellcraft. I’ll provide a chart for you right now.
|Identify a spell as it is being cast||15 + spell level|
|Learn a spell from a spellbook or scroll||15 + spell level|
|Prepare a spell from a borrowed spellbook||15 + spell level|
|Identify a spell effect that is in place||20 + spell level|
|Identify a spell that just targeted you||25 + spell level|
|Decipher a scroll||20 + spell level|
|Identify the spells cast using a specific material component||20|
Note that you would also use K: Arcana to create items as well as identify them. Many, if not most, magic items function slightly differently than their component spells. For those items that are SIAC, or otherwise exactly duplicate spells, you would still use K: Arcana because we want consistency, and also because an item is casting the spell, not a spellcaster, and different rules apply to wands and scrolls and potions and so forth. This makes a clear distinction between Spellcraft, which is entirely for spells, and K: Arcana, which covers all other aspects of magic.
Final Analysis: Best to just dump Spellcraft and use Knowledge: Arcana for all relevant things. If you must keep it, make it relevant only solely to spells. I really can’t stand the crossover between these two skills; why you use one for one thing and one for the other seems completely arbitrary to me.