Fiendish Forge (5e) - Evolved Combat, Monstrous Crafting

Created by Io Publishing

Welcome to the Fiendish Forge pre-order store! You can make late pledges or add items you'd like while we work on the book! You will be charged at a later date, along with shipping - once we're ready to ship!

Latest Updates from Our Project:

Fiendish Forge: January 2026 Update
3 months ago – Mon, Jan 26, 2026 at 01:39:24 PM

Howdy folks!

Hope everyone's year was well-rested.

Today's update is pretty straightforward: we're still internally reviewing the completed book.

Currently, we have 165 pages reviewed. Along with reviews, cleanup, and rebalancing, we're also getting more art done for the book to fill any open spots. Right now, the book is around 340+ pages and will probably grow a bit more as the table of contents and appendices finish up.

There is no release date at this time, but when there is, we will be sure to let you know. As always, the work is done when it's done, so when you have the book in your hands, it will be as complete as we could have made it.

Not much longer now. Thank you for your continued support!
Brett

Core Book Content COMPLETE!
5 months ago – Sat, Dec 06, 2025 at 05:01:25 PM

Hello everyone!

I'm thrilled to share a huge milestone with you - all monster content for Fiendish Forge is officially complete!
This includes materials, magic items, monsters, quests, and all other core book components. With this, we are now entering the final review phase before releasing the book.

What’s Left to Finish

We’re down to the final steps:
Monster Review
Our team will conduct a thorough review to correct errors, give final polish, and ensure consistency throughout the entire book.
Rulesets
These are largely complete. We are reviewing for clarity and may add one or two miscellaneous rules if needed.
Monster-Making Rules
These rules are entirely written (they were used internally to create the book’s monsters) and need to be moved into their final section of the book.

What about Playtests?

Last month, we mentioned the possibility of running one more playtest before finalizing this section of the book. After reviewing our progress, I decided to bypass last month's playtest. Since we were so close to completing the entire core book, focusing effort on another playtest felt unnecessary and would slow down our progress.
We’ve already received a lot of valuable feedback from previous playtests, as well as internal testing, and I've been pretty satisfied with the results. 

Release Window?

I am not ready to announce a release date at this time, as Io Publishing has always worked on "the book is done when it's done" - and I'd hate to let folks down with any unforeseen delays. What I can tell you is that we will be releasing the digital PDF and digital maps to our backers and pre-order customers first, before making them available to the general public. Think of this as early access for supporting our Fiendish Forge. This will allow us to get even more feedback and make any final updates before sending the book off to the printers, where it will be immortalized forever. Once the physical book is finished and in our warehouses, we will then release everything publicly. 

Thank You for Your Support

Your support and patience have brought us to the last stretch of development on Io Publishing's second major book. I look forward to sharing more as we progress into the final stages.
Thank you again for helping bring Fiendish Forge to life.

Brett

Fiendish Forge: October 2025 Update
6 months ago – Mon, Nov 03, 2025 at 03:36:54 PM

Hi everyone!  Brett here with your monthly update on Fiendish Forge!

Progress Report:

Here is where we are at:

Writing: | 90%
Design: | 85%
Art: | 98%
Total: | 91%

Progress continues, testing is good!

Running the new Elites and Bosses feels great in my games, and we've been playtesting over at the Io Publishing Discord. I feel confident and comfortable with the system we have in place, and excited as Monster designs and development continue!  Right now, I've finished with 31 out of the 49 stat blocks for the book. Elites and Bosses especially take a lot of time since they are very involved stat blocks, but we're moving at a good pace! Once the stat blocks are finished, I'll be able to move on to monster creation rules (Underlings, Elites, and Bosses) - which I'm hoping won't take as long.

November's Playtest: Madam Hush


After completing all the data for last month's playtest, we'll move on to our next release candidate, Madam Hush! I'm looking forward to your thoughts on this classic World of Io encounter.  As always, be sure to join our Discord if you're interested in being part of the playtest: https://discord.gg/e9RCf8bFke 

That's all for this month! Take care, and look forward to next month's updates!

Brett

Fiendish Forge: September 2025 Update
7 months ago – Thu, Oct 02, 2025 at 09:08:11 AM

Hi everyone!  Brett here with your monthly update on Fiendish Forge!

Progress Report:

Here is where we are at:

Writing: | 90%
Design: | 80%
Art: | 98%
Total: | 89%

Progress is moving along!

Been doing some personal tests, as well as in my streamed games, and have been satisfied with the results! I'm about half way through redesigning all the monsters. I'm hoping to be close to done (or maybe even finished) by the end of the month. Just finished a big move this September, and about to go on another trip, but once that's done, I should have more time to dedicate to Fiendish Forge.

October's Playtest: Fallen Hero

Once I'm, back from my trip, our next playtest will be the Fallen Hero! This Boss CR 10 has abilities from every class in standard 5e systems and should be an encounter with a lot of familiar variety! Look forward to it! Be sure to join our discord to participate in the playtest: https://discord.gg/e9RCf8bFke 

That's all for this month! Take care, and look forward to next month's updates!

Brett


Fiendish Forge: August 2025 Update
8 months ago – Wed, Sep 03, 2025 at 05:46:19 PM

Hi everyone!  Brett here with your monthly update on Fiendish Forge!

Progress Report:

Here is where we are at:

Writing: 90%
Design: 71%
Art: 97%
Total: 86%

New calculations for Elites/Bosses. Removal of Superboss. Added Underling.

You may notice our Design and Total % went down. This is because, after reviewing the data, I decided to reformulate Elite and Boss CR with a newer system. This means redoing every stat block in the book. Fortunately, with new systems in place, this should be feasible, especially while our art is finishing up. We've got some really cool stuff cooking from the previous month, and I think you guys will appreciate the extra time.

I will say with the new calculations, I really like the direction of all the creatures. It feels more balanced to the previous iterations that should connect well with 5e. In addition, the new sytem allows for more structure when it comes to creating your own creatures. New playtests will be coming soon this month to show off these changes, but internally, the stats feel good.

Superboss CR was removed as it troublesome. Since every GM has a different opinion of what a Superboss feels like, it led to some conflict between making a Superboss not challenging enough, to making it so powerful it was wiping parties. Ultimately felt that the removal of such a ranking was better off.

With that, I created an Underling CR! The idea with Underlings is that it should have the difficulty of 1 Player Character, allowing you to easily create a group of Underlings whose CR matches the party level. It's with my hope that GMs will be able to create encounters with ease with this new CR. 


Phase Turns are BACK and updated! (now Phase Actions)

After testing with the Legendary Action system, I got a lot of folks who were disappointed that Phase Turns were not part of creatures any more. Ultimately I was worried about multiple turns, and when effects were suppose to end. After some though and testing, I decided to combine the idea of Legendary Actions, but in an initiative order.  Effectively, this hybrid are called Phase Actions, and will include rules on how to add Phase Actions to the initiative count correctly. Unlike Phase Turns, which had a category of the type of turn, and what precise actions were taken (in which you'd have to reference in another section) - all the information for Phase Actions are right there *in* the action.  They are still actions, which means they cannot be taken when Incapacitated (much like Legendary Actions), and now we are including a Phase Action that is the turn of the creature itself, in which you would take the creature's turn as normal.  This is where all "Beginning/End of Turn" effects take place, so I'm hoping this solution will be elegant while keeping to the spirit of the previous Phase Combat.

This system would work here using an existing creature from 5e.

Adult Green Dragon (non Lair)
An Adult Green Dragon has 3 different Legendary Actions that we can easily convert into Phase Actions. Because the Green Dragon has an Initiative score of 11, we will have their turn take place on Initiative 21.  If there are 2 Phase Actions along with the Turn, I recommend adding/subtracting 10 from the Initiative count to place those Phase Actions into place. However, since there are 3 (4 in a Lair), I recommend adding/subtracting 5 - making the Phase Actions look like this in Initiative.

  • Dragon's Turn (21 - Turn). The Adult Green Dragon takes their turn as normal.
  • Mind Invasion (16). The dragon uses Spellcasting to cast Mind Spike (level 3 version).
  • Noxious Miasma (11). Constitution Saving Throw: DC 17, each creature in a 20-foot-radius Sphere centered on a point the dragon can see within 90 feet. Failure: 7 (2d6) Poison damage, and the target takes a −2 penalty to AC until the end of its next turn. Failure or Success: The dragon can’t take this action again until the start of its next turn.
  • Pounce (6). The dragon moves up to half its Speed, and it makes one Rend attack.

New Action Type: Burst Actions

Much like Legendary Actions, these Burst Actions allow a creature to do a 1/Encounter action at the end of another creature's turn. This allows the combat to stay fresh with new things continuously happening in the encounter.  Burst Actions have their own damage calculation, meaning they don't take away from the damage a creature is suppose to do during a battle (thus "Burst") - allowing a GM to spike the difficulty as necessary.  When a Burst Action is taken, another Burst Action cannot be taken until the end of the creature's turn.

Legendary Resistance Redux

Once again, we're changing up how Legendary Resistances work. Creatures with Legendary Resistances has a number of uses that they can do it with. However, the Legendary Resistance now costs something to the creature. Originally this was a Legendary Action use, but this can now alternate depending on the creature. Some creatures may activate Legendary Resistance by skipping a Phase Action, while others may activate it by taking damage inflicted upon themselves. I've been finding this system a great way for players to feel like their efforts are being rewarded, even if a Legendary Resistance is used. 

Playtests soon!

I have a lot of life changes happening this month (including a big move), along with some work events I'm attending. However, I'll do my best to get a playtest scheduled for you guys! Be sure to sign up over at our discord. https://discord.gg/e9RCf8bFke 

Brett