A Review of the Role Playing Game Supplement Sandy Petersen’s Cthulhu Mythos for 5e

Sandy Petersen’s Cthulhu Mythos for 5e by Sandy Petersen is a role playing game supplement published by Petersen Games for use with Dungeons & Dragons 5th Edition. As such, it is covered by the Open Game License and some parts are considered to be Open Game Content as a result.

The supplement is available as a PDF from DriveThruRPG for $19.99. It is also available in printed form from sites such as Amazon. The PDF is the version reviewed, although it was purchased at a reduced price during a sale, and has 419 pages. Two pages are the front and rear covers, one the front matter, three the Table of Contents, three the General Index, three the Monsters by Challenge Rating and Items/Artifacts and two the Open Game License.

Chapter 1: Using this Book explains that the supplement contains material intended to help incorporate the Cthulhu Mythos into Dungeons & Dragons, with tips on running fantasy horror games, new character options, new rules for insanity and dread in the tradition of cosmic horror, new spells, including a new subtype, items, artefacts, monsters and more.

It explains what the Cthulhu Mythos is, to those who might be unfamiliar with it, three rules to bring horror to heroic fantasy – D&D is not a natural horror game – how to use horror in a tabletop game and how to turn an encounter into an adventure.

Chapter 2: Mythos Player Character Races has five new character races. These are the Dreamlands cat, the ghoul – Lovecraftian ghouls being somewhat different – the gnorri (which may be unfamiliar; they are only mentioned in “The Silver Key”, zoog and otherworldly humans, the last being Leng folk and Tcho-Tcho. Each is covered in the same sort of detail as normal races are.

Chapter 3: Player Character Options starts with a new Wisdom skill, Yog-Sothothery. This skill is the ability to recall Mythos lore or gain a new understanding of Mythos phenomena; those familiar with Call of Cthulhu will recognise this is essentially the Cthulhu Mythos skill. Following this are class options for the various Mythos races; Dreamlands Cat, Ghoul, Gnorri and Zoog. Then there are more class options that can be used by beings of any race.

There are four new backgrounds to use; though characters of any background may get involved in the Mythos, sometimes it shapes their background directly. The new backgrounds are alienist, skilled at treating insanity and madness, Mythos cultist, someone who served in the cult of a Great Old One or Outer God, Mythos survivor, someone whose life was shattered by the Mythos, and visionary, someone who is able to sense things others cannot. Finally, there are new feats, some of them specific to the different races in this book, or connected to them in some way; all are basically Mythos-related.

Chapter 4: Insanity and Dread starts by explaining that mortal minds are limited, and Mythos entities can be more than they can face. Dread and Insanity says that these should be saved for truly dire and horrific circumstances; in a fantasy setting, adventurers are unlikely to be startled much by a dead body. Dread has a Dread Tracker with seven levels, which steadily get more debilitating. New dread given adds to dread already received, and how long the effects of dread last varies. Dread itself typically goes away with time. Various sources of dread are looked at, and the possibility that higher levels of dread can cause insanity, as discussed in the next section. Characters can attempt to resist dread and there’s an optional recommended rule in that class features and traits that grant immunity to the frightened condition instead grant dread resistance and are less affected by it.

Insanity is a long-term condition and a sidebar explains that the insanities in this chapter are not intended to reflect real-world mental illnesses but instead are supernaturally-induced conditions that affect heroes in play. It also explains that GMs will need to be aware of players’ real-life needs regarding mental illness when using the fantasy versions. Characters can attempt to save against gaining an insanity and when a new form is gained, the save DCs of exiting insanities increases. Characters can attempt to recover from insanity. There are different ways in which characters can be driven insane and a list of different kinds of insanities to gain, as well as an optional rule for using dread without insanity.

Following this is a brief look at Aklo, with a list of the creatures in this supplement with some level of familiarity with it; Aklo isn’t fully usable or comprehensible to mortals.

The Dreamlands looks at this realm that may be visited, with details on how normal dreamers enter the Dreamlands, time in it, travelling and the effects of death and injury in the Dreamlands. Whilst dying in the Dreamlands doesn’t kill the dreamer, it means they can never enter the Dreamlands again.

Chapter 5: Spellcasting in the Mythos starts by explaining that using Mythos magic can be dangerous to mortals. It then looks at a special tag some spells have, formula. Spells tagged in such a way will function even for non-spellcasters, though that certainly doesn’t mean they are safe. They can be cast normally, as a formula or, if they have a ritual tag and the character can use casting rituals, as a ritual. Casting as a formula has a risk of failure. Formula spells can be learned exclusively as a formula, though when learned as such they cannot be cast using a spell slot or a ritual. How to cast a spell as a formula is covered, with what the various options mean. A sidebar looks at Cthulhu Mythos familiars; the brain cylinder, detailed here, and the brazen head and Dreamlands cat, detailed elsewhere. List of formula spells are followed by lists of spells by class, followed by the spells themselves. The spell descriptions have new stats, related to using them as a formula, and it’s notable that there are some powerful spells here.

Chapter 6: Mythos Items and Texts starts by explaining that the chapter has a number of different Mythos-related items, often crafted by more advanced entities than humans and frequently dangerous. Adventuring Gear has various nonmagical items that might be used by those who know of the Mythos. Following this is alien technology and magic items, though the alien technology is covered in exactly the same way as magic items. This section also includes some artefacts.

Following these are some Mythos texts. The section starts with details on how to research texts and the risks of Mythos research. All books have an ability check bonus for researching the book, and many contain spells, formulas and instructions for making magical and alchemical items that are not easily noticed on first view. A list shows how common each text is.

The books themselves are then described. Each has an ability check DC, ability check bonuses, save DC and a description of the work. Depending on the work in question, it can also have formulas and other spells; most, but not all, have both.

Chapter 7: Cults of the Mythos explains that most cults centre around the worship of a Great Old One or Outer God. Cultists are typically focused on the material and immediate rewards and not an afterlife, even if they crave immortality. Eight major cults are covered, though Nyarlathotep’s cult has six different cults, given the god’s many forms. Each cult follows a similar format, with a description of the cult and the gifts that those who belong to it gain. Following this are lesser cults, of which there are eleven; these are covered in less detail and many of the cults lack gifts.

The cultures of two Mythos groups are described next. The Tcho-Tcho are a subset of humans, skilled in the Mythos and biological and otherworldly science. Details are given of their society and an assassin-enforcer. Deep ones are the other group, with information on their life cycle, habitat and relations with others.

The religion of various Mythos entities is given, with the main Mythos beings different groups worship. Following this are details on the standard D&D races and their relations with the Mythos, as well as the entities they are most likely to follow.

Chapter 8: Great Old Ones, Outer Gods and Others starts by explaining that the various beings in this chapter are enormously powerful and distort reality. They are not monsters and though the climactic battle with one results in combating something with stats, these confrontations are only with some minor aspect of the entity. A sidebar looks at alignment; these entities are not good or evil in the traditional sense, though their cults are usually evil and usually chaotic, so the entities are treated as such.

Instructions are then given on how to read the stat block of an Elder Influence. They are divided into types, have specific areas of concern, an alignment associated with the Influence, the primary sources of material on the creature, their cult, its favoured weapon and most common symbol, as well as their temple and worshippers and their servitors. Influence is the effect an Elder Influence has on an area and Nucleus is a physical manifestation of the entity. An influence can have multiple stages, each getting worse, as each stage has an effect on anything in the area. How such beings can be defeated – or, rather, a local portion of them can be – is covered as well as running combat. Given the abilities of an Elder Influence, characters will need to defeat one quickly or become lunch. Possibly literally. Twenty-six Elder Influences are then extensively detailed; Nyarlathotep naturally has several forms.

Chapter 9: Mythos Monsters is the bestiary and starts with a couple of adventure hooks before moving onto the creatures. Each is described in typical fashion; many have multiple variants, some of them extremely deadly.

Appendix 1: Nonplayer Characters has stats for various humanoid NPCs who will most likely be encountered in cults serving Elder Influences.

Appendix 2: Encounter Tables is, as it suggests, a list of encounter tables for various environments.

Sandy Petersen’s Cthulhu Mythos for 5e in Review

The PDF is bookmarked with major and minor sections linked. The Table of Contents is to a similar level of depth and is hyperlinked. The three indices then provide more detail. Navigation is good. The text maintains a two-column format and appeared to be free of errors. There are a variety of colour illustrations, up to full page in size. Presentation is good.

Dungeons & Dragons as a whole, and especially the superheroic fantasy of 5th Edition, really isn’t suited to the kind of horror stories associated with cosmic horror. This does attempt to get around that in a number of ways, by the introduction of new rules that makes things harder for characters and by such as the Elder Influences being mere fractions of the god-like creatures in question, so the characters never have the chance to kill off a god, yet can still face something incredibly dangerous. However, with it being 5th Edition, the odds of coming out of a combat with an Elder Influence victorious are going to be higher than in, say, Call of Cthulhu.

Now, this game does do a decent job of making 5th Edition more dangerous and converting the Cthulhu Mythos to the system, but if you really want a dangerous cosmic horror game, this probably can’t be recommended. It’s still got too much 5E DNA in it that makes such a game easier than it would be. If you want a cosmic horror game where it’s less horror-based and more heroic, then this does work. Sandy Petersen’s Cthulhu Mythos for 5e can be found by clicking here.