Ad-Hoc Skill Check Modifiers for NPCs

[Matthias]

AD HOC SKILL CHECK MODIFIERS FOR NPCs
(older version orig. posted in r.g.f.d)

I have encountered a few situations as DM where the player characters have
decided to check out the local shops. By necessity they invoke several opposed
rolls from these NPCs which did not exist moments before. I have been hoping to
be able to guesstimate the skill check modifiers for these NPCs, however, rather
than come up with abstract DC's from the general table of DC's listed in the PHB
or DMG.

I have been working on skill check modifier tables that would take into account
the NPC's probable character level, their class, whether they are using a class
or cross-class skill, and chances of how specialized they have become in that
particular skill.

For purposes of this system, I have limited NPCs to being either 1st, 5th, 9th,
13th, or 17th level. These particular levels give you a max.-ranks-value which
is evenly divisible by 4. So a character that gains 2 SP/level (ignoring Int-mod
& racial bonus SP) will get (character level + 3) x 2 SP (referred to the
character's base SP total).

Let's say that a character's skills can be classified by priority, where the
priority determins the number of SP a given skill has. Let us also say that
given 3 priority levels (low, medium, and high), they are proportional as
follows: 14. Thus low-priority skills will have N SP, med-priority skills 2xN
SP, and high-priority skills 4xN SP. (I talk about SP only, not actual ranks,
because some characters of a given class such as Fighter may consider
cross-class skills to be important enough to gain SP in, such as Tumble. In such
cases the actual no. of ranks would be 1/2 the SP put into them, but the
proportion of assigned SP to the max ranks of the skill will usually remain the
same as for class skills, excluding multiclass characters.)

Now limiting NPCs to the specific levels given above, lets us deal with base SP
that exist in multiples of 8. This lets us divide the base SP for a given
character into 8 packets of SP to assign to different skills regardless of
character level, where each packet has 1/4th the character's max ranks in SP (or
1/8th of their base SP). So a Ftr13 will have 32 base SP, and will have 8
packets of 4 SP to distribute among any skills that would be important to him.

A high priority skill would get 4 packets, making that particular skill maxed
out. A medium priority skill would get 2 packets, and a low priority skill would
get 1 packet. After this point, any skill points gained from a positive Int
modifier ((CL+3) x Int mod) or from being human (CL+3) would be assigned where
desired, presumably with the NPC's profession or specialty in mind.

NPC getting 2 SP/level will have anywhere from 2 to 8 skills with SP assigned
them (not counting the extra skills getting SP gained from high Int or racial
SP). Classes giving 4, 6, or 8 SP/level will of course have 4 to 16, 6 to 24, or
8 to 24 skills with SP.

Now there are different permutations for low, medium, and high-priority skills
based on this system.

L: low-priority skills (MR/4 SP each)
M: medium-priority skills (MR/2 SP each)
H: high priority skills (MR SP each)

With classes getting 2 SP/level, there are 9 permutations of priority:
L/M/H (number in each priority)
8/-/- (8 total)
6/1/- (7 total)
4/2/- (6 total)
4/-/1 (5 total)
2/3/- (5 total)
2/1/1 (4 total)
-/4/- (4 total)
-/2/1 (3 total)
-/-/2 (2 total)

With classes getting 4 SP/level, there are 25 permutations:
L/M/H
16/-/- (16 total)
14/1/- (15 total)
12/2/- (14 total)
12/-/1 (13 total)
10/3/- (13 total)
10/1/1 (12 total)
8/4/- (12 total)
8/2/1 (11 total)
8/-/2 (10 total)
6/5/- (11 total)
6/3/1 (10 total)
6/1/2 (9 total)
4/6/- (10 total)
4/4/1 (9 total)
4/2/2 (8 total)
4/-/3 (7 total)
2/7/- (9 total)
2/5/1 (8 total)
2/3/2 (7 total)
2/1/3 (6 total)
-/8/- (8 total)
-/6/1 (7 total)
-/4/2 (6 total)
-/2/3 (5 total)
-/-/4 (4 total)

With classes receiving 6 and 8 SP/level, there are many more permutations (I'm
guessing 49 and 81, respectively). One might consider having an even number of
skills of each priority level, which would pare down the number of permutations
for 2-SP/level classes to 5 and the number of permutations for 4-SP/level
classes to (apparently) 11.


At this point, you have a system that could be used to generate skill sets for
NPCs a little more quickly than it would take to generate a player character
with totally customized skill ranks. Assuming you fleshed out a set of tables
with the calculated number of SP per packet a given class would receive at a
given level, and you would have all the info you'd need to assign SP on the fly
for a new NPC.

IMO the above system is a bit more flexible than what the MM suggests about
assigning SP to new monsters, which is what this system is partially based on.
(That is, assign (HD+3) SP to a number of skills for the monster according to
how many skill points per level they receive by creature type.)

However, what I am really looking for is a set of tables that could abstract the
process still further. By limiting the SP assignment process, we might be able
to increase the level of abstraction more easily.

So far I have had some success, but these tables basically depend on a few key
questions I am having trouble determining:

What are the odds that a character of a given class & level would have put at
least one SP into a given skill if it is a class skill?

What are the odds that a character of a given class & level would have put at
least one SP into a given skill if it is a cross-class skill?

Once we know whether a character has put SP into a skill, what are the odds the
character made it a low-priority, medium-priority, or high priority skill?

After that, once we know the class, level, whether the skill gained any SP, and
what priority the skill was given, we can determine exactly how many SP (and
ranks) the NPC would have, and therefore present the player character with a
somewhat realistic opposed roll.

Opinions? Suggestions? Advice?

 

[S'mon]

My approach would be just to give the guy a +5, +10, +15 or +20 bonus depending on whether they were a mediocre (+5), good (+10), great (+15) or legendary (+20) in their field.

 

[S'mon]

Oh, you might want to check out the Quick NPC System in my sig.

For NPC skills, you're typically looking at a chap with a Good (+2) relevant stat & maxed ranks, plus possibly Skill Focus if its his core profession, so a dedicated 1st-level Expert might have +9, 2nd-level +10, etc. In fact Level+8 is a good guide as to the highest the skill is likely to be, though the average shopkeeper is more likely level+5. Maybe roll a d8, for Level+d8.

 

[Matthias]

My approach would be just to give the guy a +5, +10, +15 or +20 bonus depending on whether they were a mediocre (+5), good (+10), great (+15) or legendary (+20) in their field.

That's basically the same as assigning static DCs for tasks, which I'm hoping to improve upon.

 

[Matthias]

Oh, you might want to check out the Quick NPC System in my sig.

For NPC skills, you're typically looking at a chap with a Good (+2) relevant stat & maxed ranks, plus possibly Skill Focus if its his core profession, so a dedicated 1st-level Expert might have +9, 2nd-level +10, etc. In fact Level+8 is a good guide as to the highest the skill is likely to be, though the average shopkeeper is more likely level+5. Maybe roll a d8, for Level+d8.

Assigning a 1d6 or 1d8 or whatever might be the thing to do depending on how one wants to deal with skill priority and such, but I will have to see how the current biz pans out before I drop back to randomized modifiers.

 

[Matthias]

This is related to my ongoing project of ad-hoc skill check modifiers.

I have three formulas for determining the percentage of skill points that a player character of a given class and _low_ level would have put into cross-class skills versus their class skills . (At higher levels a character can better afford to spread his SP around a little so that will skew the results.)

Please look at each set of probabilities and pick the one that seems to fit your own experiences the best. Avoid critiquing specific scores by class, but if the majority of the numbers seem off for a given set then rate that set poorly. I purposefully omitted the methods used, to make it a 'blind test'.


METHOD #1
Bbn- 30% of SP are cross-class
Brd- 40% " " " " " " "
Clr- 20% " " " " " " "
Drd- 30% " " " " " " "
Ftr- 20% " " " " " " "
Mnk- 30% " " " " " " "
Pal- 20% " " " " " " "
Rgr- 40% " " " " " " "
Rog- 50% " " " " " " "
Sor- 20% " " " " " " "
Wiz- 20% " " " " " " "

METHOD #2
Bbn- 19% of SP are cross-class
Brd- 49% " " " " " " "
Clr- 15% " " " " " " "
Drd- 23% " " " " " " "
Ftr- 12% " " " " " " "
Mnk- 28% " " " " " " "
Pal- 15% " " " " " " "
Rgr- 34% " " " " " " "
Rog- 49% " " " " " " "
Sor- 11% " " " " " " "
Wiz- 20% " " " " " " "

METHOD #3
Bbn- 42% of SP are cross-class
Brd- 12% " " " " " " "
Clr- 20% " " " " " " "
Drd- 34% " " " " " " "
Ftr- 26% " " " " " " "
Mnk- 24% " " " " " " "
Pal- 20% " " " " " " "
Rgr- 42% " " " " " " "
Rog- 42% " " " " " " "
Sor- 28% " " " " " " "
Wiz- 10% " " " " " " "

Your participation will be appreciated.

 

[S'mon]

Hm, as far as PCs go, the only ones I've seen spending skill points cross-class would be those taking cc ranks in Spot. This is only likely if the PC already has a WIS of 10+ and they want to bump their Spot chance up with points that would otherwise be 'wasted' on little-used skills. Otherwise PCs don't take CC skills, so I wouldn't think NPCs would either. NPC Experts get a free choice of 10 skills so they likely never need to.