John Carter of Mars RPG: Jeddak of Jeddaks Era Supplement Guide
By Modiphius US | Published: 2026-10-17
Category: Buying Guides
Decide whether the Jeddak of Jeddaks era supplement and a White Ape STL miniature belong in your John Carter of Mars RPG campaign, with clear fit rules and trade-offs.
Quick answer
Buy the Jeddak of Jeddaks Era Supplemental Rulebook if your group already plays the John Carter of Mars RPG and wants to move play into the later Barsoom novels, especially The Mastermind of Mars and Skeleton Men of Jupiter. Skip it if you only own the core book and have not yet run a campaign, because the supplement assumes you already know the 2d20 rules. Add the White Ape STL only if you print miniatures at home and want a tabletop threat that matches Barsoom's savage wildlife.
What the Jeddak of Jeddaks supplement actually adds
This is not a standalone game. The Jeddak of Jeddaks Era Supplemental Rulebook gives you narrator advice for running the themes and tone of the later John Carter novels, plus guidance on the plots of the last eight books in the series. That means you get campaign material for stories set after the classic early adventures, including The Mastermind of Mars and Skeleton Men of Jupiter. If your group has already played through the core book's default era, this is the bridge to stranger, more political, and more science-fantasy-flavored Barsoom stories.
Who should buy the era supplement first
The supplement rewards a group that has finished at least one short arc in the core John Carter of Mars RPG. It assumes familiarity with the 2d20 system and with Barsoom's factions, so a brand-new narrator will get more value from the core book before adding this. If you are the narrator and you want to adapt specific late-period novels, the plot guidance is the main reason to buy. If you are a player who only wants new character options, check whether your group's narrator plans to use the era at all before spending.
Where the White Ape STL fits a Barsoom campaign
The White Ape STL is a print-at-home 3D file, not a physical miniature. It represents a savage beast from the dying world of Barsoom, which makes it a natural tabletop threat for wilderness or ruin encounters. Buy it if you already have access to a 3D printer and want a creature that matches the setting's tone. Do not buy it expecting a painted or pre-printed figure, and do not buy it as a first purchase if your group plays theater of the mind.
How to sequence your John Carter RPG purchases
Start with the core book, run a short adventure, then add the Jeddak of Jeddaks era supplement when your group wants the later novels. Add the White Ape STL only after you know your table uses miniatures and you can print them. If you also play Star Trek Adventures, keep those purchases separate; the Allies and Adversaries sourcebook is a pre-order with shipping expected late September 2026 and a complimentary PDF on purchase, so it will not help a Barsoom campaign.
Decision rules for the Jeddak of Jeddaks era
- You have run at least one core-book arc: Buy the era supplement now. It assumes 2d20 familiarity and gives you late-novel plots and narrator advice that the core book does not cover. Best next purchase for active John Carter groups.
- You are still learning the core rules: Delay the supplement. Run the core book first so the era advice has a campaign to attach to. Core book first, era book second.
- You want a physical monster miniature: Do not buy the White Ape STL. It is a print-at-home file, so you must have a 3D printer and finishing supplies. Only buy the STL if you print at home.
- You want late-novel plots without new rules: The supplement focuses on narrator advice and plots of the last eight novels, not a new standalone rule set. Buy for story guidance, not for a new game.
Product facts
- John Carter of Mars: Jeddak of Jeddaks Era Supplemental Rulebook: The Jeddak of Jeddaks Era Supplemental Rulebook provides an in-depth look at the later eras of play for the John Carter of Mars RPG, with narrator advice on the themes and tone of the era and the plots of the last eight John Carter novels including The Mastermind of Mars and Skeleton Men of Jupiter. If your group wants to move beyond the core era, this is the book that gives the narrator concrete plot and tone support for late-period Barsoom stories.
- John Carter of Mars - Print at Home - White Ape STL: This 3D print product features the white ape, a terrifying, savage beast from the dying world of Barsoom, and is a print-at-home STL file rather than a physical miniature. You need a 3D printer and the willingness to print and finish the model yourself; it suits tables that already use miniatures for combat encounters.
Is this supplement right for your table?
Best for
- Narrators who already run the John Carter of Mars RPG and want late-era Barsoom plots
- Groups that have finished a core-book arc and want The Mastermind of Mars and Skeleton Men of Jupiter material
- Players who print miniatures at home and want a White Ape threat for encounters
Not for
- New groups that do not yet own or have not played the core book
- Players who want a physical, pre-printed miniature rather than an STL file
- Anyone looking for a standalone game or a new rules system
