Call of Cthulhu <--> Deadlands conversions

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Allan Seyberth

Jul 27, 1998, 3:00:00 AM7/27/98
From a post on the listserv by one Afterburner <>
(reposted here with his permission)


I'm in the midst of converting an old, out of print Call of Cthulhu
scenario to Deadlands (and will put it up on my webpage when I'm done).
Doing so requires some method of converting from the flat percentages used
by CoC (and, in fact, used by every other Chaosium product that I know of)
to the Fistful o' Polyhedrons mechanic of Deadlands. I've come up with a
method that serves the purpose quite handily, and I thought I'd share it
with the rest of the class.

The system works on two assumptions:

1) The Deadlands dice mechanic is based on an average TN of 5.
2) It's easier (and less munchkiny) to figure out the dice value of
Aptitudes, and then make the Traits match the common die type of the
Aptitudes than it is to figure out the Traits first and then try to wedge
the skills into the particular die type.

That said, here's a nifty chart which matches a Deadlands dice value
it's chance of making a TN of 5, with a maximum of 5d<x>. Note that the
granularity is pretty big on the low end of the scale and gets finer as you
get to the high end of the scale.

25% 1d4
33% 1d6
44% 2d4
50% 1d8
53% 3d4
56% 2d6
60% 1d10
67% 4d4
67% 1d12
68% 3d6
75% 2d8
76% 5d4
80% 4d6
84% 2d10
85% 3d8
87% 5d6
89% 2d12
92% 3d10
93% 4d8
95% 3d12
97% 5d8
97% 4d10
99% 5d10
99% 4d12
99% 5d12

The first step is to pick a Deadlands Trait (I usually start with
Deftness, since it's the first one listed in the rulebook) and then sift
through the Call of Cthulhu character for skills which match the skills
under that trait. I break the Call of Cthulhu skills down as follows (and
leaving out the obvious ones, like Climb -> Climbin'):

Accounting -> Professional: Accountin'
Anthropology -> Academia: Anthropology
Archaeology -> Academia: Archaeology
Astronomy -> Science: Astronomy
Bargain -> Persuasion, or make up a new skill (Hagglin', perhaps)
Botany -> Science: Botany
Camouflage -> Sneak, or make up a new skill (Hidin', perhaps)
Credit Rating -> Dinero edge
Cthulhu Mythos -> Academia: Weird West or Academia: Occult
Debate -> Persuasion, or make up a new skill (Debatin', perhaps)
Diagnose Disease -> Medicine: General
Drive Automobile -> Horse Ridin'
Electrical Repair -> Tinkerin'
Fast Talk -> Persuasion
First Aid -> Medicine: General, or make up a new skill
(Medicine: First Aid, perhaps)
Geology -> Science: Geology
Hide -> Sneak, or make up a new skill (Hidin', perhaps)
Jump -> Base Nimbleness, or make up new skill (Jumpin', perhaps)
Law -> Professional: Law
Library Use -> Academia: Library Use
Linguist -> Academia: Linguistics
Listen -> Big Ears edge, or make up a new skill (Listenin', perhaps)
Make Maps -> Professional: Cartography
Mechanical Repair -> Tinkerin'
Operate Heavy Machinery -> Drivin': Steam Wagon
Oratory -> Tale Tellin'
Pharmacy -> Professional: Pharmacist
Pickpocket -> Filchin'
Pilot Aircraft -> Drivin': Ornithopter
Psychoanalysis -> Professional: Psychology
Psychology -> Scrutinize
Sing -> Performin'
Spot Hidden -> Search
Throw -> Throwin': Blunt object (rock, small ball, etc)
Treat Disease -> Medicine: General
Treat Poison -> Medicine: General
Zoology -> Science: Zoology

Special note: SAN -> Guts

Once the skills have been determined for each trait, the die type
(hopefully) be obvious. If not, you'll have to make a judgement call as to
which die type should apply. Once you do, change the Coordinations for the
skills to match the percentage as closely as possible.

Once you've determined the die type, divide the Call of Cthulhu
characteristic by the max score of 18 (or 21 if it's EDU) to get a
percentage, and then compare that percentage on the chart above and try to
match the die type as closely as possible. The following chart is what I
use to convert amongst the various characteristics and Traits:

Deftness = DEX
Nimbleness = (DEX + STR)/2
Strength = STR (duh!)
Quickness = (DEX + INT)/2
Vigor = CON

Cognition = INT
Knowledge = EDU
Mien = APP
Smarts = (INT + POW)/2
Spirit = POW

To take a particular example, one of the characters I'm converting
has the following skills which would go under Deftness:

Throw 81%
.45 Revolver 80%
.32 Derringer 80%

This is pretty convenient, so I look up 80% on the table and get 4d6.
combine the two weapons skills into "Shootin': Pistol 4d6" and the throwing
skill into "Throwin': Blunt Object 4d6". Since these are the only skils
for this character that would fall under Deftness, the character's deftness
will be a d6. The Call of Cthulhu DEX characteristic for this character is
14, and 14 divided by 18 gives a percentage of 78% Looking on the chart,
there is no 78%. But there is an 80%, which is 4d6, which matches the die
type from the skills. So the character now has:

Deftness: 4d6
Shootin': Pistol: 4d6
Throwin': Blunt object: 4d6

Moving on to Nimbleness, we find the following skills apply:

Drive Auto 40%
Hide 40%
Sneak 66%
Blackjack 78%
Fist 90%

Matching percentages results in:

Horse Ridin': 2d4
Hidin': 2d4
Sneak: 4d4

The Blackjack and Fist skills are tricky because in Deadlands they
both go
under Fightin': Brawlin'. However, I'm willing to split the difference and
say that this character has a general fighting skill of 84%. Since there's
nothing on the chart for d4 past 76%, I'll fudge a bit and give the
character a 6d4 in Fightin': Brawlin'. The character's DEX is, as
mentioned, 14, and his STR is 13. Adding the two, dividing by two, and
rounding down gives us 13, which divided by 18 equals 72%. Which is closer
to 76% (5d4) than it is to 67% (4d4). So this character now has the

Nimbleness: 5d4
Horse Ridin': 2d4
Hidin': 2d4
Sneak: 4d4
Fightin': Brawlin': 6d4

Just continue on in this vein for all the skills and characteristics.
Edges and hinderances can be gleaned from the descriptions of the
characters. For instance, this particular character is described as having
a "rotund physique." So he gets the Big 'un(-1) hinderance. But he's also
described as being a "hard-bitten law officer of nearly 40 years
experience", so he gets the Brave, Nerves o' Steel, and Lawman(3) edges.

This isn't a brainless conversion system; the person making the
will often have to make judgement calls. But so far it's worked pretty
well for this scenario.

Hope you find it useful.


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