I've never really sat down and explained what exactly it is that I'm designing. This post rectifies that.

A History

The birth of "2d10 System"

2d10 System was first born some time in late 2016 (my first semester of college) when I was a player in a 5e campaign that was really pushing D&D to the breaking point of its systems. At the core of everything was sort of D&D 5e's two fatal flaws:

1. Social mechanics are basically nonexistent;
2. Dungeon crawls, raids, resource management, etc are built on extremely weak foundations.

Both myself and the GM of that game (who is fairly private about his identity on the internet) were really into Burning Wheel at the time, and so the initial question was just

Well what if we try to make Duel Of Wits work in D&D?

For those not in the know, Duel Of Wits is Burning Wheel's system for hashing out debates between characters. It's pretty in-depth, and calls on a lot of skill variety/mechanics that just aren't reasonably replicable in D&D. It became clear to us pretty quickly that whatever it was, this needed to be more than just a hack of D&D.

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2d10 System was about the game you would expect coming out of an opinionated college freshman who'd bitten off way more than he could chew.

On one hand, 19-year-old me was pretty inspired when it came to picking 2d10 (an attempt to merge Stars Without Number's skill (2d6) and attack (d20) rolls into one), but it wouldn't be until years later that I realized the power of making advantage stack.

The main thrust was that I was making a D&D-style class based game that was trying to equally balance exploration, negotiation, and combat. There were 27 classes (way too many), some of which were basically combat-focused and some of which were basically negotiation-focused, and a few which struck a balance. The idea was that within a party you could expect to have people who excelled at each of the subsystems.

It was a total mess:

1. The negotiation system tried to solve some of Duel of Wits' stiltedness problems, but utterly failed to do that and honestly ended up way wonkier. Making serious mechanics for negotiation feel good/like more than GM fiat while making sure that they don't hamper the conversation is really hard lmao, I still don't have it totally solved. I am cooking, tho.
2. Combat still had the D&D problem of feeling like dudes walking up and whacking each other with basic attacks every round. I also committed to simultaneous action resolution without really considering what needed to change about D&D combat to make that work.
3. I confused "every system should have mechanical depth and be deliberate" with "every system should be as complicated and nitty-gritty as combat", which is an easy mistake to make but still very much a mistake.

I ran a number of playtests during this time, which introduced my original set of species via player selection. (There weren't rules for species at the time, so I told players to pitch me on whatever). Kobolds, Minotaurs¹, Shadow-men (still haven't settled on a name for em), Revenants, and Cat-girls (no longer part of the game; if I do cat people later they probably won't be like anime cat-girls).

After about a year, work slowed and the project became a solo one on the writing front (though my would-be co-author remains an editor). Between 2018 and mid 2020 I worked on the game in fits and starts, but never really got it out of its original funk.

The Redesign

Some time in like, august? of 2020, something clicked. I went on a designing spree, starting to really put together the game systems as I think of them now.

The main thing is that at a certain point I started thinking less "what if I could make Duel of Wits work" and more

What if D&D was designed after PBTA instead of before PBTA?

This is a much broader design question, but at the same time it's a much more focused one. I made sweeping changes to every part of the game over the course of a month or two. Looking back on my work, I realized that I had done a double ship-of-theseus to the game text: first from D&D to 2d10 System, and then from 2d10 System to something else entirely. And so it was that I called the game Project Theseus; though for all I know, I'll rename it yet again before it's truly done.

Basically every design decision is a direct response to something I didn't like about D&D or something that could work better, but it's far from a hack. The game feel is extremely different; this is the game of someone who grew up reading Rothfus and Martin and Hiromu Arikawa. My sense of what fantasy is has much deeper roots in the mechanics of politics and character melodrama than that of the old-school wargaming nerds reading Jack Vance and JRR Tolkien.

The design as it stands now

There's kind of too much to talk about in one chost, so instead I'm going to make a bulleted list that acts like a table of contents of all the chosts I have written (or plan to write) about my design and why it is the way it is. This list is in no particular order. Some (about half) of these design ideas were bouncing around in the pre-2020 era, some were not.

• The GM is fully treated as a player; rather that exist outside/alongside the rules, the GM is bound by them and given an explicit list of things which they can do.
• I retooled the stats to give the game a distinct feel and fix what I found inherently broken about the mental stats of D&D. In particular, this change was necessary to start really making any sort of negotiation mechanics hold weight.
• Combat is built on opposed rolls rather than rolls-to-hit against a static armor class.
• The combat system got its turn broken into phases of simultaneous resolution for different types of action. (I would later discover that I'm not the first one to come up with this. Justin Alexander had done it first. He's become one of my favorite RPG/GMing writers; you should go check him out at that there link.)
• Melee combat was improved by making different weapons play fundamentally differently, inspired by my experience with Historical European Martial Arts.
• I stripped the number of classes down significantly, keeping each class capable in combat while cementing the classes' social role(s) with social mechanics.
• I made advantage stack, allowing for meaningful group check mechanics and the vibe of crunch without the number-crunching.
• The game is now structured as crawls within crawls, with a full mechanical framework for exploration.
• The skills are grouped into base-skills and subskills to allow characters to have specific specialties but general competence over a broad range.
• Species are built of traits rather than stat bonuses, encouraging both more interesting game design and a more anti-racist narrative frame.
• Experience is given out for doing the things that I want to encourage players to do, rather than by pure GM fiat or pure combat.
• Instead of a single HP bar that represents everything, you track your physical strain, mental strain, wounds, trauma, and exhaustion as separate influences on your current state.
• Every class that can cast magic casts fundamentally different magic through a fundamentally different mechanism.
• The social skills run deeper than Persuasion/Deception/Performance.
• For the best interests of both healing magic and religion, I separated the two from each other.
• Conditions are a core part of the game experience rather than a collection of fringe elements like they often end up being in D&D. In particular, every damage type (physical and mental) is capable of inflicting a relevant condition in the right circumstances.

I'll add more to these bullets over time as I write chosts, but this is already enough ambition for today.

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1. The first character anyone other than me rolled up was a Minotaur named Theseus. While the game isn't exactly named for him, it's not not named for him either. When I finally gave the game a working title in 2020, he's what inspired me to consider the Ship-of-Theseus when I looked back at what I'd written and realized it was almost totally a different game than the one I started.