d20-magic

Calculate d20 spell save DCs and spell attack modifiers.

3|Updated Dec 14, 2025

Search Tags:#ritual #cantrip #concentration #spell-slot #spellcasting #d20-magic #DC

Ready to run

npx skills add https://github.com/rjroy/adventure-engine-corvran --skill d20-magic

💬 Prompt for ChatGPT / Claude Chat▼

Please help me install this Agent Skill.
Skill: d20-magic
Source: https://github.com/rjroy/adventure-engine-corvran/tree/main/d20-system/skills/d20-magic
Command: npx skills add https://github.com/rjroy/adventure-engine-corvran --skill d20-magic

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve?

This Skill provides spellcasting guidance for the d20 system, including Spell Save DC, Spell Attack modifiers, Concentration, spell slots, cantrips, rituals, and spell preparation.

Core Features & Use Cases

Core formulas for Spell Save DC and Spell Attack.
Spell Slots progression and class focus.
Cantrips scaling and Concentration rules.
Ritual Casting, Spell Preparation, and component requirements.

Quick Start

To resolve a spell attack, roll 1d20+modifier and compare against target AC; to compute DC, use 8 + Proficiency Bonus + Ability Modifier; refer to spell descriptions for effects.