Learn to DM: Spellcraft Vs Knowledge Arcana

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Charon
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Learn to DM: Spellcraft Vs Knowledge Arcana

Post by Charon »

Another thing that seems to crop up all too often is confusion over when something should be Knowledge Arcana or Spellcraft.

The rulebooks give some clear examples of Spellcraft. Identifying spells being cast, identifying auras when using detect magic, identifying magical items... I'm starting to see a theme here. But why isn't this just magical knowledge?

The best way to understand the difference is to look at the difference between knowledge and practical skills and we can do that by comparing other skills that remove the magical element and use real world examples we can better wrap our heads around.

Knowledge Geology might give me a deep knowledge of rock formations and layers of the earth and whatnot. But when I set out to go prospecting and make my fortune, I'm probably going to find that Profession Miner will be far more useful in the reality of being underground digging through the rock searching for gold. Conversely, a miner is great at mining around and doing his thing, ensuring the earthworks are stable and avoiding gas pockets and such, but does he really appreciate the history. Does he actually know how many years or how much pressure it takes to produce marble? No, because that is simply knowledge.

Knowledge Sailing might furnish me with knowledge about boats. I could identify sections of a boat, know my port from starboard and probably much deeper things like the liveries or building styles of different nations, the different types of ships available and their cargo space, gun ports, how many sails, top speed, combat prowess, etc.
But when it comes to actually sailing a ship, doing the rigging, navigating by the stars, not puking over the edge, actually knowing one ship inside out well enough to navigate in the fog simply by feel. Well now this is Sailcraft, ie Profession Sailor. And conversely, he might not know enough to realise that the Tyrolean sloop emerging from the other side of the fog is actually flying the wrong flag and is a Marvolian ship in disguise, something my knowledge sailing would certainly help with.

Now let's apply this to magical examples. The things the rulebooks say are spellcraft are because this isn't simply knowledge.
Identifying a spell being cast could be considered knowledge, if you had all the time in the world to slow it down and work it out. But you don't, you have a second and that's why it's spellcraft. Identifying auras or magical items is an analysis of a magical effect. You're working backwards, trying to figure out what it does rather than simply know what it does. You are applying skill.
So what does fall under knowledge arcana?
Well, anything you can simply know. If I need to burn through some rope and I turn to the party wizard to see if he has any tricks that could help, knowledge arcana would allow him to know precisely which spells produce fire and more than that, whether they will actually burn inanimate rope or not. An arcana roll can produce information about how the spells work mechanically, for example if an enemy casts invisibility and disappears and the party ask, how long will that last? A wizard could confidently say, well, assuming they are of similar power to myself, approximately this long... even if they don't have the spell learned.
They could also produce knowledge about magical things in general. You might need spellcraft to figure out a potion is a potion of levitate but if you know you have a potion of levitate then arcana will determine what it does and for how long. If you know this enemy just dropped a hat of disguise then arcana will be the skill that tells you how it works.

Another good example is the player bullshit. Every time a player tries to manipulate a spell in a way that isn't intended.
Can I use mage hand to distract this enemy?
Arcana will give you the answer, yes or no.
Should the player attempt it, then spellcraft will be useful to manipulate the spell to have the desired effect.
For example, can I fire a fireball down the chimney?
Knowledge Arcana would reveal that yes, you can, and no spellcraft roll will be necessary, because fireball is a tiny dot that becomes a fireball at the point of impact, not a hadoken that springs fully formed from your hands.

In summary then, Knowledge Arcana is just that. Things that you know. Information about magic.
If the thing you're trying to do involves a more practical application of magic or magical theory then it's spellcraft.

Hopefully this helps DMs and players alike finally understand the difference.
"No one is useless in this world who lightens the burden of it to anyone else." - Charles Dickens.

“Choose not to be harmed and you won’t feel harmed. Don’t feel harmed and you haven’t been.” - Marcus Aurelius
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