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RPG Worlds & Adventures

Deep worldbuilding, thoughtful game design, and practical tools for creating unforgettable tabletop experiences. Step behind the DM screen with Circle of One.

What We Offer

From practical GM tools to deep worldbuilding guides, Circle of One provides resources for every aspect of your tabletop journey.

GM Tools & Guides

GM Tools & Guides

Practical, battle-tested tools for Game Masters. From tactical combat systems to campaign planning frameworks, designed to enhance your table's experience.

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Advanced 5E Content

Specialized resources for Level Up: Advanced 5E. Combat mechanics, character options, and campaign advice tailored to this enhanced ruleset.

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About Neill Whyborne

Tabletop RPG designer and worldbuilding enthusiast

I've been playing tabletop RPGs since 1979. That's nearly 50 years of campaigns, character sheets, and dice rolls across every edition of D&D, Traveller, Rolemaster, RuneQuest, and countless other systems. I'm not the perfect DM—my friends will tell you that—but I have good ideas, and I've learned what works at the table.

My focus is on worldbuilding and mechanics. I love systems with crunch and detail, especially when it comes to action-based monsters and NPCs that feel alive. I believe in complexity where it makes sense, simplicity where it doesn't—no grind, just purposeful depth.

Circle of One started in October 2025 as a way to share what I've learned: practical tools, thoughtful analysis, and resources for Game Masters who want to run better campaigns. Whether you're designing a monster, building a world, or solving a mechanical problem, I'm here to help you think deeper.

Areas of Expertise

  • Worldbuilding - Geography, politics, cultures, and the systems that make worlds feel real
  • Mechanics Design - Action-based systems, detailed NPCs, and crunch that serves the story
  • Campaign Planning - Practical frameworks for running adventures that players remember

Design Philosophy

"Crunch without grind. Complexity where it makes sense. Simplicity where it doesn't."

Every rule, every mechanic, every system element should serve the game. No busywork. No unnecessary complexity. Just purposeful depth that makes your table better.

Systems I Know

D&D (All Editions)TravellerRolemasterRuneQuestLevel Up: A5E

Currently exploring: Blades in the Dark

Ready to Level Up Your Game?

Explore my articles, products, and tools designed to make your campaigns better.

Latest Article

Mastering
Date unavailable
5 min read

F is for Failing Forward: The Antidote to the Dead End

In F is for Failing Forward, we dismantle the biggest threat to campaign momentum: the dead end. A blown deception check or a botched negotiation shouldn't stop the story; it should escalate the tension. Discover how to keep your plot moving by transforming failed rolls into messy compromises, forcing players down dangerous alternative routes, or taxing their hard-earned time, wealth, and reputation. We will explore how to ensure that even when the dice betray you, the narrative never stops moving.

Featured This Week

Discover a curated external tool to enhance your tabletop experience

Level Up Gateway

System Tools

The official character builder and campaign management tool for Level Up: Advanced 5th Edition. Create characters, manage parties, build encounters, and collaborate with other players and narrators.

a5eadvanced-5echaracter-buildercampaigncollaboration

This featured tool rotates weekly. Visit our Resources page to explore all available tools.

Featured Release

Spotlight: Latest Adventure Module

Discover our newest and most acclaimed product, crafted for Game Masters who demand excellence

The First Journey: Upriver in Hepmonaland (5e)

The First Journey: Upriver in Hepmonaland (5e)

New release - be among the first to review

A concise, table-ready toolkit for running upriver travel adventures in the world of Greyhawk. Focused on the jungle rivers of Hepmonaland, this supplement offers practical guidance on navigation, the use (and loss) of local guides, jungle hazards, exhaustion, and interactions with river communities. Fully compatible with D&D 5e (2014 & 2024) without introducing new subsystems.

What's Included

  • Practical guidance on jungle river navigation
  • Local guide mechanics and consequences
  • Jungle hazards and exhaustion rules
  • River community interactions
  • Appendix: The Umo river-dwelling people as guides, contacts, or obstacles

Available exclusively on DM's Guild Marketplace

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Have questions or want to collaborate? We'd love to hear from you.