I recently had occasion to write up a quick introduction to Cthulhu
Eternal for a group I play with, and thought it might be more broadly
useful.
Short version: it's what you get if you kick an Australian in the
teeth and tell him to smile about it. (Chaosium changed their Call of
Cthulhu licencing policies with the effect of driving out small
independent publishers, since their options were to go down to the
Miskatonic Repository with a huge cut to Chaosium and a strict cap on
total sales, or up to the peer company level with large minimum sales
and a custom licence agreement.)
Cthulhu Eternal is an OGL!free ruleset for Lovecraftian and allied
gaming for which anyone can publish material. Its rules are largely
derived from the 2016 Delta Green and from 2011's Legend, the rule
set derived from RQ2 that Mongoose produced after they lost the
RuneQuest licence. It is largely compatible (not quite a drop-in
replacement, but nearly so) with Call of Cthulhu (first to sixth
editions).
There is no single master rulebook but a series of bare-bones system
reference documents, one for each era of play. (They have different
skill lists, professions, etc.) These are freely available. Some are
also published in prettier and more illustrated versions.
The Open Cthulhu Mythos Project has worked to produce stats for
spells, monsters, tomes, etc., based strictly on the original stories
rather than on Chaosium's additions, and those are available in two
guises: the free Open Cthulhu Mythos SRD (text only), and HPL's
Book of Yog-Sothothery (prettier and more illustrated).
There are also various adventures published for the system, generally
paid-for.
A rules summary emphasising points of difference from Call of
Cthulhu:
Most rolls are percentile, but damage and sanity loss can need other
dice.
Five stats, on a 3-18 scale, and a stat roll is percentile against
stat×5. Derived stats are Sanity, Hit Points, and Willpower. (I
generally roll 4d6 take highest 3 for each stat and arrange as you see
fit, but that's up to the GM.)
You'll pick an Occupation, which gives you some fixed skills, and a
list of skills that you can boost with skill picks. You can also spend
those skill picks on some other things.
Skills are percentile, with default values, not influenced by stats.
Easy or hard tasks can give ±20, occasionally ±40 to the roll, but
most rolls are unmodified. Matching percentile digits on a success is
a critical success; on a failure is a critical failure.
You tick a skill when you use it and fail, and having a tick at the
end of an adventure gets you +d4 to that skill.
1-2 HP is unconscious and a risk of dropping stats; 0 HP is dead. 1-2
Willpower is frazzled and at skill penalties; 0 WP is unconscious.
There is Sanity. You lose it when you see scary or unnatural things:
-
lose 5 points or more in a single roll, temporary insanity (flee,
struggle or submit).
-
reach your Breaking Point (usually 80% of starting Sanity), gain a
new mental disorder.
-
reach 0 sanity, permanently out of play.
As part of character generation you will have a Resources level (this
generally starts low and you can trade in skill picks to kick it up a
bit). This is notionally divided into "at hand" (first six levels),
"stowed" (next six levels, might be in a vehicle) and "stored"
(anything more, in a home base). Roll against your currently available
resources × 5 to produce a useful item; at GM discretion, doing so may
temporarily reduce that rating by a point or more. In any case, your
resources rating is also the number of times per adventure you can do
this.
You will also have Bonds (again, which can be boosted by skill picks).
These are connections with people (Individual Bonds) or groups
(Community Bonds). The higher the rating, the stronger the
relationship. You can reduce them to bolster yourself against sanity
loss in various ways (they give you mental strength but the
relationship is damaged). Generally Bonds may not matter hugely in a
one-shot, though Community Bonds are an indicator of how well your
character is respected within a particular group (to some extent
replacing the way "Credit Rating" skill gets used in Call of
Cthulhu; there's also an Etiquette skill which covers social
fitting-in).
Combat is mostly roll to hit, roll for damage. If you are doing
something other than melee, get attacked, and haven't yet acted this
round, you can abort that prospective action to dodge or fight back
(get a defence roll).
Some particularly powerful weapons have a Lethality rating instead of
Damage, which is the chance that a human target is killed outright
when hit. If they don't get killed by it, add the 2d10 of that failed
lethality roll and they take that as damage.