So just as a recap:
quote:
You can use this skill to identify monsters and their special powers or vulnerabilities. In general, the DC of such a check equals 10 + the monster’s CR. For common monsters, such as goblins, the DC of this check equals 5 + the monster’s CR. For particularly rare monsters, such as the tarrasque, the DC of this check equals 15 + the monster’s CR or more. A successful check allows you to remember a bit of useful information about that monster. For every 5 points by which your check result exceeds the DC, you recall another piece of useful information.
As a general rule of thumb, if it's a "basic D&D staple" monster (i.e. orcs, goblins, skeletons...the kind of monsters that show up EVERYWHERE in EVERY SYSTEM) those I qualify as "common" monsters.
Otherwise by default I use the "uncommon" difficulty of 10+CR. If it's a singular monster, one that isn't native to the plane of existence, or if I'm pulling it out of a 3rd party book that's when I go for the "rare" difficulty of 15+CR.
In general here is how I deliver information:
Special Defenses > Special Attacks > Miscellaneous Information & Abilities
Creature Type > Subtype > Specific Creature
What that means is that if the PC rolls and gets 3 pieces of information, I start with the general creature immunities and work down to the specific creature, prioritizing defenses over attacks over "other".
So take a gelatinous cube. This is a common monster (staple of D&D) so DC is 5+CR3 = 8
For 1 piece of information I reveal all the ooze special traits (mindless, immune to precision damage, blind, immune to mind-affecting spells etc.)
For the second piece I would reveal that gelatinous cubes are immune to electricity
3 pieces = it secretes a poison that paralyzes anything it touches
4 pieces = it engulfs and digests its pray whole
5 pieces (i.e. rolled 28+) I would reveal that its acid doesn't dissolve stone.
On PBP for common monsters it's pretty moot because everyone just looks them up on the d20pfsrd so I usually am fairly creative with descriptions of my "special" monsters so they have to make knowledge checks just to even figure out WHAT they're fighting :P