Converting 5th Edition Fantasy to the SIEGE Engine - Conversion guidelines by Jason Vey

Oct 5, 2026

Conversion guidelines for moving 5th Edition Fantasy adventures from a 5e-style framework into the SIEGE Engine for play in Castles & Crusades or Amazing Adventures. The document explains the guiding principle of using direct SIEGE equivalents, then details how to adapt skills, ability checks, and saves by mapping 5e DCs to SIEGE challenge classes (CC) using CL/CB and conversion formulas. It also covers handling advantage and disadvantage, converting magic items (including bonuses and identify rules), and offers an approach to monster conversion while maintaining encounter fidelity and intended challenge.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages7

Reading Time18 min

AccessFree to download

THE GUIDING PRINCIPLE

ADAPTING SKILLS, ABILITY CHECKS, AND SAVES

UNDERSTANDING CHALLENGE CLASS

UNDERSTANDING DC

CONVERSION METHOD

DEALING WITH ADVANTAGE AND DISADVANTAGE

CONVERTING MAGIC ITEMS

CONVERTING MONSTERS

Converting 5th Edition Fantasy to the SIEGE Engine Conversion guidelines by Jason Vey More and more players are moving from 5e fantasy to simpler systems that offer a great deal more in terms of allowing players to expand their imagination and explore boundless and unlimited worlds, not fettered by skill lists, feats, and “optimal character builds.” Among the more popular of these games is Castles & Crusades, from which 5e clearly draws a great deal of inspiration. This document will allow you to convert any 5th Edition Fantasy adventure quickly and easily to the SIEGE Engine for use in your Castles & Crusades or Amazing Adventures game. While the guidelines may not result in a 100% direct conversion when compared to published versions of the monsters in each source, they will maintain the fidelity of the adventure and the general challenge level of the checks and creatures involved. One cannot account for completely different design principles in two games, nor can one account for differing interpretations – since C&C and 5e were not built from one another, the best one can hope for in conversion is an approximation. We hope this document makes the transition easy for you. THE GUIDING PRINCIPLE The core, guiding principle in all aspects of conversion is this: if it has a SIEGE Engine equivalent, use it. Leather armor in 5e becomes leather armor in the SIEGE Engine. An orcin 5e becomes a SIEGE Engine orc. A Cloak of Elvenkind in 5e becomes a SIEGE Engine Cloak of Elvenkind. Always keep this in mind and it will vastly simplify your conversion. ADAPTING SKILLS, ABILITY CHECKS, AND SAVES Both 5e Fantasy and the SIEGE ENGINE use ability or attribute checks as the core of their system. Everything in both systems work on the idea that when the Castle Keeper, or CK (the Game Master), asks for a check you roll a d20, add applicable bonuses based on an ability score / attribute, and try to hit a target number. In 5e, this target number is called the Difficulty Class, or DC. In the SIEGE Engine, it is called a Challenge Class, or CC. UNDERSTANDING CHALLENGE CLASS In Castles & Crusades, the challenge class is determined by adding the Challenge Level, or CL, to the Challenge Base, or CB. All characters in Castles & Crusades have Primary Attributes, set by their class and choice, and Secondary attributes, which are all the others. The Challenge Base for Primary attributes is 12, and for Secondary attributes is 18. The second step in calculating challenge class is determining the conflict’s challenge level, which is the level of difficulty of the challenge involved. Challenge levels range with easy being 1 to 5, difficult, 6 to 10, very difficult is 11 to 15 and Heroic, near impossible actions require a challenge level of 15 to 20 or even higher. For example, let’s say the characters are trying to climb up a ragged cliffside. The Castle Keeper, or CK (the Game Master), considers this moderately difficult and assigns a CL of 5, also declaring that it is a Strength check. Characters for whom Strength is a Prime need a 17 (12+5). Characters for whom Strength is Secondary (or non-Prime) need a 23 (18+5) . Usually, the CK will simply tell players, “It’s a CL 5 Strength Check.” The player in question may then say,“I got a 20, Prime,”indicating success, or “I got an 18 non-Prime,” indicating failure. Or they’ll just say,“made it!” or “nope.” UNDERSTANDING DC 5e Fantasy games use a flat challenge, simply applying a difficulty class. Easy tasks have a DC 10 (the default) . Moderate Tasks are DC 15 or thereabouts. Difficult Tasks range from 18-20. Heroic tasks range up to DC 25, and so forth. CONVERSION METHOD The base method to convert DC to CL is simply to subtract 10 from the DC. Thus, a DC 17 task becomes a CL 7 challenge. This method is less than precise, however, when the DC goes higher than 17. If you don’t mind tasks being a bit easier in C&C, you can just ignore the discrepancy and go. If, on the other han

FAQs

What is the guiding principle when converting from 5e to the SIEGE Engine?

Use a SIEGE Engine equivalent whenever one exists. Keep concepts like armor and named items aligned by substituting direct equivalents rather than redesigning everything from scratch.

How do you convert a 5e DC to a SIEGE Engine challenge class (CL)?

A baseline method subtracts 10 from the DC (e.g., DC 17 becomes CL 7). For higher DCs, a more accurate adjustment adds 2–5 based on ranges like 18–19, 20–21, 22–23, and 24–25.

How should magic items be handled during conversion?

Most magic items convert directly if a SIEGE equivalent exists. Items that grant advantage on a check should typically become +4 or +5 in the SIEGE Engine, and identification rules differ (attunement isn’t needed; identify is required).

Oct 5, 2026

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