I thought, if I made an NPC of say, Witch level 4, that would be CR 4. But that can't be right, because that would make one level 4 character, a fair fight for a TEAM of level 4 characters.
Please help, I've always been confused by this stage of creating encounters. :)
From looking up examples from different classes, it appears that in Pathfinder a 4th level witch from a standard power race would be CR 3 (class level minus 1), and a 4th level adept would be CR 2 (class level minus 2). I do not recall seeing this explicitly spelled out anywhere, but every official NPC stat block I have seen seems to follow that pattern.
Adding NPCs: Creatures whose Hit Dice are solely a factor of their class levels and not a feature of their race, such as all of the PC races detailed in Races , are factored into combats a little differently than normal monsters or monsters with class levels. A creature that possesses class levels, but does not have any racial Hit Dice, is factored in as a creature with a CR equal to its class levels –1. A creature that only possesses non-player class levels (such as a warrior or adept) is factored in as a creature with a CR equal to its class levels –2. If this reduction would reduce a creature's CR to below 1, its CR drops one step on the following progression for each step below 1 this reduction would make: 1/2, 1/3, 1/4, 1/6, 1/8.
Also note that the PCs are expected to win.
"Normal" challenge fights are not meant to be "fair". They are, in fact, heavily weighted in the PCs favour.
Adding NPCs: Creatures whose Hit Dice are solely a factor of their class levels and not a feature of their race, such as all of the PC races detailed in Races, are factored into combats a little differently than normal monsters or monsters with class levels. A creature that possesses class levels, but does not have any racial Hit Dice, is factored in as a creature with a CR equal to its class levels –1. A creature that only possesses non-player class levels (such as a warrior or adept) is factored in as a creature with a CR equal to its class levels –2. If this reduction would reduce a creature's CR to below 1, its CR drops one step on the following progression for each step below 1 this reduction would make: 1/2, 1/3, 1/4, 1/6, 1/8.
Thanks everyone, that's cleared things up a lot! Great links too, I'll have a proper read when I get time.