The D20 Swings
TTRPG’s are games that use rules as guides to allow fantastic situations to occur in a way that board games cannot because the rules are more rigid. The D20 has been used in D&D since 1974 on its creation. It was not the main thing in the mechanics. But it was there. Its role grew bigger and bigger in each coming edition. Finally sitting as the main mechanic for the 3rd edition game created 26 years later in 2000. Additionally, the d20 system started that same year. Its core feature is that you roll a d20 and add some numbers called modifiers. Modifiers is a common TTRPG word that describes in numerical terms how much better you are at something than the average person.
Consider the following situation: There’s a creature on a balcony shooting arrows at you. You want to stop them but you only have a sword. You want to use your sword to cut the chandelier rope and soar to the balcony. Your GM (Game Master) might ask you to roll an acrobatics check for this. There will be a DC (Difficulty Class) associated with this which, depending on the GM may or may not tell you. When asked to roll you roll a D20; the result on the die gets added to your modifier for Acrobatics. You succeed by meeting or doing better than the DC. You fail if your total roll is below. In action you roll a 14, and add your +4 Acrobatics for a total of 18. The DC was 15 and you succeeded. “Your rogue sees the quickest way up to the goblin is the chandelier. She cuts the rope and grabs on with one hand. Whoosh; in an instant you find yourself on the balcony face to face with a goblin shooting arrows. The chandelier shatters in the middle of the floor below.”
In play the d20 is rolled almost anytime there is a risk of failure. Featured heavily in combat, when exploring, or when engaging with non player characters (NPC’s). Skills lists and abilities help to round out the particulars of what a given character is good at. On any given roll there is a 55% chance of rolling a 10 or higher and a 45% of rolling lower. There is a lot of “swinginess” to that roll and the chance of failure is higher than you’d like. The stronger or more adept the thing you are fighting, tracking, influencing, is the higher chance for failure. Stories are told on these successes and failures. That creates drama and that, for most fans of d20 system games, is where the fun is found.
D20, D&D, and Changes
Dungeon and Dragon’s 3rd edition and 3.5 edition (a popular edition following just 3 years after 3rd ed.) popularized the d20 as the go to roll. Before this players used hit tables and there was a lot of wonky math. THAC0 (To hit at Armor Class 0) is derided a lot as one such hit table. THAC0 was never as complicated as people make it seem it was, but the d20 definitely simplified the rolls. It was so popular that Wizards of the Coast released a Systems Reference Document separate from the 3.5 rules defining the d20 system.
That system brought on a slew of new games. The two most popular were d20 Modern and 2009’s Pathfinder (now known as Pathfinder 1e). Modern was a set of rules that used the d20 system and used modern ideas and settings. (D&D 3.5 was a fantasy setting game.) In 2008 with D&D releasing 4th edition and changing the licensing from the D20, the company Paizo took a shot at maintaining what existed from 3.5 with its rules for everything and started Pathfinder. That licensing change was more restrictive and Paizo took advantage of the old one. Today, Pathfinder is the second most popular TTRPG in the space and clings to its d20 roots strongly, though they have made enough changes to get away from the d20 system and really have created their own brand.
The D20 Today
Because of changes in licensing d20 systems have popped up on their own. After Dungeon and Dragon’s unpopular Game System License for 4th edition, Wizard of the Coasts 5th edition created the Open Gaming License. The OGL allowed for 5e content to be made from outsiders. Additionally, a shared marketplace was created for even more openness to rules with the DM’s Guild. Games using D20’s no longer utilize the d20system logo as they use the OGL instead.
That being said, the core of the d20 system is what drives D&D today. It drives pathfinder and other games as well. Tales of the Valiant, Level Up Advanced 5e, Pathfinder 2e, and most of the OSR (Old school renaissance) use a d20 and modifiers. Modiphius’s 2d20 system features 2 icosahedron dice simply and elegantly along with skills and abilities. Modiphius’s Fallout RPG is specifically reminiscent of a d20 system with a large skill list and different dice being used for damage as most d20 games do.
Shadowdark
13th age
Shadow of the Weird Wizard
Shadow of the Demon Lord
Dungeon Crawl Classics
Pathfinder 1e
Pathfinder 2e
Dungeon and Dragon’s 3rd, 3.5, 4th, 5th, and 2024 5th all feature the d20 as a core mechanic. 5th edition and its offshoots add onto the mechanics of d20 with bounded accuracy, advantage, and disadvantage. These rules have been adopted widely as positive for the game. Bounded accuracy means that the Armorclass stays in reach for monsters and characters alike throughout the various levels of the game. Advantage means you get to roll 2 d20’s and choose the highest roll to add to your modifiers. Disadvantage means you take the lower of the 2 rolls and add your modifiers.
Play a TTRPG
While the d20 is at the core of many games, the idea of role playing and what that entails has spawned a slew of other games that use fantasy, modern, and other settings to tell fantastical stories. Savage Worlds, Gurps, Basic Roleplaying system, and Powered by the Apocalypse all use the pillars, exploration, social interactions, and combat in their games. They all stem from 1974’s Dungeons and Dragons Game. They are wonderful in their own right and offer a lot of varied themes and mechanics. The hobby, the industry continues to grow. There is a lot to be excited for with both the d20 and other games that incorporate fantastical thinking and interesting mechanics.
There are some GM’s at StartPlaying Games who specialize in playing most of the games talked about here. games. I encourage looking at any game that strikes your fancy.D&D has a 50 year history now and is largely responsible for all the other TTRPG (Tabletop Role Playing Games) that have come since. Born from wargaming, a love of Tolkien, and the game Chainmail 1974’s Dungeons and Dragons revolutionized gaming and created a new way to game that most people are familiar with today. A game played with polyhedral (many sided) dice and most specifically the D20 or 20 sided dice (known mathematically as icosahedron). The D20 sits at the core of D&D.
Adam McDivitt is a father of 3 boys, professional GM, and a full time therapist. His love of D&D was reignited when his son asked him to help with a game 4 years ago. Since then he has learned a number of new systems and fell in love with TTRPG systems outside of 5e. Follow him on bluesky gmadam.bsky.social he posts there sometimes.
