OSR Commentary Combining Castles & Crusades with Swords & Wizardry rpg

 Combining Castles & Crusades (C&C) and Swords & Wizardry (S&W) is one of the easiest cross-system integrations in the Old School Renaissance (OSR) space. Both games are rooted in early editions of Dungeons & Dragons (OD&D and AD&D) and share near-identical core mechanics.

Integrating the two gives you the best of both worlds: S&W’s lean, flexible retro-clone content and C&C’s clean, unified SIEGE Engine task-resolution system.

Core System Differences at a Glance

Feature	Castles & Crusades	Swords & Wizardry
Task Resolution	SIEGE Engine (d20 + level + modifier vs. Target Number 12 or 18)	Single-d20 checks, d6 hazard rolls, or GM rulings
Armor Class	Ascending AC (10 + Armor)	Ascending or Descending (varies by printing, usually Ascending default)
Saving Throws	Attribute-based saves using the SIEGE Engine	Single unified Saving Throw number
Monster Stats	HD, Hit Points, AC, Movement, Attacks, Special Abilities	HD, AC, Movement, Attacks, Saving Throw, Special

1. Mechanics & Task Resolution (The SIEGE Engine)

The easiest hybrid framework uses C&C’s SIEGE Engine as the mechanical engine and S&W as the source content repository.

• Base Mechanics: Keep C&C’s Primary vs. Secondary Attributes.

  • Primary Attributes have a Base Challenge Class (CC) of 12.

  • Secondary Attributes have a Base Challenge Class (CC) of 18.

  • Target Number = Base CC + Challenge Degree (difficulty or target’s HD/level).

• Skills & Non-Combat Tasks: When an S&W module calls for a thief skill or general check (e.g., listening at doors, searching, climbing), use C&C’s SIEGE check:

  $$\text{d20} + \text{Attribute Mod} + \text{Level} \ge \text{Target Number}$$

2. Converting Saving Throws

S&W uses a single unified saving throw number (e.g., a 1st-level Fighter saves on a 14+), while C&C uses SIEGE checks tied to specific attributes (Strength for poison/paralysis, Dexterity for breath weapons/traps, Wisdom for mental spells, etc.).

How to Convert S&W Saves to C&C

1. Identify the effect causing the save (e.g., Fireball, Poison, Charm).

2. Assign the relevant C&C Attribute:

   • Strength: Physical restraint, crushing, forced movement.

   • Dexterity: Traps, dragon breath, area-of-effect dodge.

   • Constitution: Poison, disease, drain, endurance.

   • Intelligence: Illusion, psychic attacks, mental confusion.

   • Wisdom: Charms, fear, holy/unholy magic, perception.

   • Charisma: Banishment, possession, social/pact magic.

3. Have the character roll a standard SIEGE check against the caster’s Level/HD as the Challenge Degree.

3. Monster & Encounter Compatibility

S&W monsters are virtually 100% plug-and-play in C&C with minor adjustments:

• Hit Dice & Attack Bonus: In both systems, a monster’s Hit Dice equal its base attack bonus/level equivalent.

• Armor Class: Ensure both use Ascending AC.

  • If using older S&W material with Descending AC (DAC):

    $$\text{Ascending AC} = 19 - \text{Descending AC}$$

• Special Abilities & SIEGE Checks: If an S&W monster forces a special roll, turn it into a C&C SIEGE save using the monster’s HD as the Challenge Degree added to the Base CC (12 or 18).

4. Spells & Magic Items

• Spell Levels: S&W spells translate directly into C&C spell slots. S&W’s magic is slightly lighter and less codified, which fits C&C well.

• Spell DC: If an S&W spell forces a save, use the caster's level as the Challenge Degree for the target's SIEGE check.

• Magic Items: S&W magic items can be used in C&C without alteration. Variable bonuses (+1 to +3) function identically in both systems.

Recommended Blending Approaches

1. "C&C Core + S&W Adventure Modules" (Most Popular):

   • Run C&C rules exactly as written.

   • Run S&W adventure modules (e.g., Rappan Athuk, Tomb of Abysthor) straight off the page without prepping conversions in advance.

2. "S&W Style + C&C Class/Race Separation":

   • Use S&W for fast, lightweight combat and single-save simplicity.

   • Import C&C’s race and class structure to give players more distinct character options and primary attribute choices.