A quick round-up and summary of different RPG games engines, super-condensed and (over) simplified
It’s a wiki-post, so you can add your own directly to this list!
D20 Games
Players roll a d20 and add relevant skill and abilitity modifiers. A result higher than an activity’s difficulty (DC) indicates a success at performing that action.
Different varieties of mechanics, economies, and character guidelines exist across titles.
Examples
- Dungeons & Dragons
- Pathfinder/Starfinder
- Shadow of the Demon Lord
- Castles & Crusades
- Hundred Dungeons
- Dungeon Crawl Classics
2D20 Games
Players sum their character’s relevant skill modifiers in order to determine a “target number”, then roll 2d20 (at minimum, some in-game factors may allow for more) and compare the results to the target number, with rolled values lower than the target constituting a “success”. The difficulty of a task determines how many successes are needed to complete the task.
Examples
- Star Trek Adventures
- Fallout: the Roleplaying Game
Powered by the Apocalypse
The outcome of a character Move is determined by rolling 2d6 and adding any relevant modifiers. Results fall into one of three categories: failure (low roll), partial (weak) success, or full (strong) success (high roll).
Examples
- City of Mist
- Avatar: Legends
Storyteller System
Character abilities and skills determine the number of d10s to roll for an action, and the entire pool is rolled. The number of dice displaying a number greater than or equal to the “success” value (defined by the game) indicates the favorability of the outcome.
Examples
- Vampire: the Masquerade
- Werewolf: the Apocalypse
Dread
Non-trivial character actions succeed depending on the player’s ability to move and place a number of blocks in a tower-stacking game commonly sold under the brand name Jenga.
Examples
- Dread
Basic Role-Playing System
Players roll percentile dice (2d10, effectively a d100) and compare the result to a fraction of the character’s related skill to determine the outcome of the action. Successes occur when the roll result is less than or equal to the character’s related skill value. More difficult tasks reduce the target number for success by some fraction of the character’s skill value. The intensity of successes and failures may be determined by the difference between the roll result and the difficulty target.
Examples
- Call of Cthulhu
- RuneQuest
The One Ring Engine
For each attempted action, players roll the d12 Fate die and a number of d6 Success dice equal to the character’s related skill. The summed results are compared to the Target number; values less than the Target indicate a failure, greater than or equal is a success.
Examples
- The One Ring
The “Free League” System
The player taking an action rolls a pool of d6s equal to the character’s related skill. The action succeeds if a certain number of the rolled dice display a specified value (varies by game).
Examples
- Tales from the Loop
- Vaesen
“Cars and Aliens” System
Actions with a risk of failure are resolved by rolling a pool of d6s indicated by the related character trait. The highest single-die result is compared to a table of outcomes ranging from total success to a failure that worsens or complicates the situation.
Examples
- The Last Caravan
Adventure Game Engine (AGE)
Players use 3d6 to determine the outcomes of tests. Of their pool of d6s, one is visually distinct and is treated specially. Different AGE games apply different names to this die, variously calling it the “Stunt”, “Drama”, or “Dragon” die - the Special Die. A character’s relevant modifiers are added to the result of the dice roll and compared to a Target Number (determined by the Game Master) to determine success or failure at the test. The result of the Special die determines the degree of success at the test - a 1 is barely succeeding, while a 6 represents an outstanding level of success. When any two of the 3d6 show matching results, the character earns a number of Stunt Points equal to the value on the Special Die; these points may be spent to employ one or more stunts that provide additional benefits or special moves.
Examples
- Dragon Age Roleplaying Game
- Fantasy AGE
- Modern AGE
- The Expanse Roleplaying Game
- Blue Rose: The AGE Roleplaying Game of Romantic Fantasy