2d20 mod, Part 4: Subsytems

Part 4 Subsytems

Pretty much every 2d20 variant has it’s own subsystems. This will just be a short overview – get the games to see more detail!

MC3 – Dark gifts and Light Arts

MC3 has two forms of magic and both work in a similar way. Each “spell” has a Difficulty, duration, target and effect. You roll vs the difficulty to achieve the effect.

Infinity -Infowar and psywar.

Infowar is basically hacking. There are zones for a system and rules for discovering zones, accessing the zones, countermeasures (ICE) and actions. Characters can have different software/programmes installed which achieve different effects. It can be complicated at times but works pretty quickly in play.

Psywar is a mix of social combat and networking. The rules for social actions and attacks make sense and work well. The rules for networking less so. How can you access a zone if you can’t physically or digitally talk to them? It’s weird, but simple enough to ditch and stick with the social combat.

Conan – Displays and Sorcery

Displays are a small subsystem used in combat to intimidate enemies based on having renown or having completed certain feats. It’s basically a series of extra actions you can take with requirements, but it’s fun and works well with source material.

Sorcery in general works like MC3. Spells have difficulty, duration and effect but they can also have a resolve cost to spend to cast.

JCoM – Renown

JCoM doesn’t really have subsystems which involve rolling dice, but does have Renown. Essentially you gain renown for accomplishing things in game which means people respect them and then you can earn accolades and titles via your Renown.

Star Trek – Scientific Discoveries and Developments

This is a great system for solving problems just like in the media. The players choose the characters’ roles for a problem, then characters suggest solutions, picking one and performing an extended test, eventually finding the correct solution and solving the problem. It’s neat, simple and works.


Dishonoured has a whole bunch of small subsystems. There are separate rules for stealth, although these are very short. There are rules for intrigue which is social combat and networking. Both of these have tracks, where you need to achieve multiple successes on the track to succeed over time. Then there are the void rules. This includes bonecharms, small items which can be found or created and then used for small benefits. And there are powers which cost runes to learn, void points to activate and provide special abilities. There are a small amount of these, but it would be handy to have rules on making your own!

Dune – Dueling, Skirmish, Espionage, Intrigue

Dune has a number of subsystems related to conflict. All involve different zones, different maneuvers and/or actions and use of assets. 

Achtung! Cthulhu – Magic

There are 4 sets of magic in A!C. 3 of the sets are similar; you have a difficulty to beat, a specific skill to use, a health cost to cast and then the effect of the spell with associated momentum spend. Spells are also split into classes such as attack, control and divination. Then there are rituals which have multiple steps to cast and rules for miscasting.

So there are subsystems in every game. Some are more involved, and some could easily just be replicated with the standard rules. But it’s a good example of both how versatile 2d20 can be and how it can be made to work for a  specific genre or setting. A base 2d20 wouldn’t need any subsystems, but then it;s easy to add on subsystems for magic or hacking for example.

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