Open Cthulhu HPLed SRD Release 1.0a Credits The Open Cthulhu HPLed System Reference Document (SRD) v1.0a draws heavily upon two OGL rulesets for d100 roleplaying: the Delta Green RPG System (sometimes called the “Misery Engine”) and the Legend System by Mongoose Publishing. It uses only the open game content parts of those systems. For details of the Cthulhu Mythos it draws upon OGL material from the Eldritch Tales OSR game and the Cthuloid Bestiary for OSR Games. This edition only references Mythos entities created by H.P. Lovecraft and generic horrors – no references to creations by other authors are included, explicitly or by allusion. Our purpose in creating the Open Cthulhu HPLed SRD is to provide a fully‐OGL ruleset for Lovecraftian gaming in common eras and settings. The rules provided here can be used as‐is to power gritty and deadly games of investigative and cosmic horror. Or, if you are a game designer, you can use these rules as a platform on which to build your own games. Remix this content however you wish! Project Coordinator: Christian T. Rosen ([email protected]) Contributing Writers (new content): David Konrad, Lena Hardaev, Michel Masó, Paul Franzese, Chris Rosen, Michelle Bernay‐Rogers, and Francis Lim. The Open Cthulhu HPLed SRD is copyright © 2019, under the Open Gaming License v1.0a Product Identity: This file contains NO items considered to be Product Identity under the OGL. Everything in the file is Open Content and is thus usable in other games, providing the attached OGL license remains intact. Contents Introduction ............................................................................................................................................ 1 Structure of this Book ......................................................................................................................... 4 Open Cthulhu Rules (Player Section) ....................................................................................................... 5 Rolling the Dice ................................................................................................................................... 5 What About Miniatures? .................................................................................................................... 5 Investigators ............................................................................................................................................ 5 What Makes an Investigator? ............................................................................................................. 6 Creating an Investigator ...................................................................................................................... 6 Detailed Description: Statistics ........................................................................................................... 8 Detailed Description: Derived Attributes ............................................................................................ 9 Detailed Description: Profession ...................................................................................................... 10 Detailed Description: Allocating Skills ............................................................................................... 12 Detailed Description: Skills................................................................................................................ 13 The Game .............................................................................................................................................. 22 Using Skills ......................................................................................................................................... 23 When to Make Skill Tests .................................................................................................................. 23 Success and Failure ........................................................................................................................... 25 Opposed Tests ................................................................................................................................... 26 Assistance .......................................................................................................................................... 27 Chases ............................................................................................................................................... 27 Improving Skills ................................................................................................................................. 27 Magic Points and Mental Exhaustion ............................................................................................... 28 Combat .................................................................................................................................................. 30 The Combat Round ........................................................................................................................... 30 Attack Rolls........................................................................................................................................ 32 Defense Rolls ..................................................................................................................................... 34 Damage ............................................................................................................................................. 35 Lethality Rating ................................................................................................................................. 37 Protection in Combat ........................................................................................................................ 40 Other Threats to Life and Limb ......................................................................................................... 41 The Aftermath ................................................................................................................................... 44 Sanity ..................................................................................................................................................... 45 Threats to SAN .................................................................................................................................. 45 Insanity and Disorders ...................................................................................................................... 47 Temporary Insanity ........................................................................................................................... 48 Disorders ........................................................................................................................................... 49 Permanent Insanity ........................................................................................................................... 52 Resisting Insanity .............................................................................................................................. 53 Recovering Sanity .............................................................................................................................. 54 Running Open Cthulhu (Keeper Section)............................................................................................... 57 Customizing Open Cthulhu for Different Settings ................................................................................. 57 Step 1: Researching the Setting ........................................................................................................ 57 Step 2: Adjusting the Open Cthulhu Skill List .................................................................................... 57 Step 3: Creating New Professions ..................................................................................................... 59 Step 4: Available Weapons and Technology ..................................................................................... 62 H.P. Lovecraft’s Dreamlands ............................................................................................................. 62 Magic and Tomes .................................................................................................................................. 66 Tomes of the Mythos ........................................................................................................................ 67 Casting Spells .................................................................................................................................... 71 Powers of the Cthulhu Mythos ............................................................................................................. 73 Encountering a Mythos Power .......................................................................................................... 73 Mental Contact with the Infinitely Alien ........................................................................................... 74 Coming Face‐to‐Face with a Living God ............................................................................................ 75 Mythos Powers from Fiction ............................................................................................................. 76 Creatures of the Cthulhu Mythos ......................................................................................................... 79 Other Creatures and Horrors .............................................................................................................