I've been toying around with a new version of the Advantage/Disadvantage mechanic in 5e, an option which will be included in my upcoming adventure: Revelry in Torth. I was after something a little less "swingy", so that having Advantage would definitely be advantageous and the burden of Disadvantage would have a bit of sting in its tail without being utterly disastrous. Inspiration hit earlier this afternoon!
When a character has a distinct edge or significant, favorable circumstances, he has Advantage on an attack or skill (pretty much any d20 roll). Advantage yields that character a +4 bonus to his attempt. If the result is a natural 1, the player can re-roll. Although, if another natural 1 occurs, it stands. The gods have spoken.
When a character has significantly unfavorable circumstances or acts at a handicap, he has Disadvantage. This yields a -4 penalty to his attack or skill (almost every type of d20 roll). If the result is a natural 20, the player must re-roll, accepting whatever the consequences shall be. However, if a second natural 20 comes up, it has been ordained by the gods!
Re-rolls also inherit the +/- 4 modifier. However, a natural 1 is always an automatic failure while natural 20's mean guaranteed success. *
Those working side by side or cooperatively have "Parallel Advantage/Disadvantage", each character rolling as described above, respective to his favorable or unfavorable circumstances.
If the GM feels that a certain amount of Advantage and Disadvantage exist simultaneously, they cancel each other out. In such cases, roll normally. However, something called "Antagonistic Advantage" is possible.
For example, let's say two opponents are locked in mortal combat. One has Advantage due to his enchanted sword while another has Advantage because of his specialized training. Antagonistic Advantage is in effect if there is no disadvantage at play. Similarly, opponents with Disadvantage (one being extraordinarily clumsy and the other stabbing in the dark, literally) have Antagonistic Disadvantage. In either case, there is no cancellation - those having Advantage retain their bonus while those with Disadvantage apply their penalty until circumstances change.
Feel free to give players a choice prior to rolling, they may decide to either use 5e's A/D system as written or my O5R alternative. Please post your feedback below and leave a comment if you playtest this new mechanic.
* Extra special thanks goes out to Danielle, my beautiful wife who sees through the awesome to find imperfections, obscure conclusions, and missing pieces.
Authored by Venger Satanis