The core dice mechanic of DXD, the engine used by the Sarna Len role-playing game, is the use of 2 six-sided "Base" dice combined with possible additional "Modifier" dice to perform Tests whenever the outcome of some action initiated by or initiated against a player-character is unknown or unpredictable.

• These dice rolled and scored against a fixed Target Number or "TN" such as 7+.

  • Each character may apply "dice modifiers" or "DMs" by the use of a contextually determined Attribute DM, Skill DM, and Trait DM. 

  • There can be various other DMs such as from a character's Background which can be used, as well as DMs from debilitating Conditions which a character is experiencing.

  • The Game Master and the players can negotiate which combinations, or more, may affect the Test results. 

• The dice are rolled, and the DMs are added to determine the Test Score total.

  • Modifier dice can be Bonus or Penalty dice. 

  • The Bonus dice replace the lowest of the Base dice, and the Penalty dice replace the highest of the Base dice.

  • Bonus and Penalty dice cancel each other; discard both. This is known as "flattening".

• Matching or exceeding the TN generates a "pass" and allows the desired action or event to occur. Otherwise, the Test "fails" and some repercussions are introduced by the GM which solidifies the failure, but also moves the narrative or story forward.

The Average TN is 7+. 

Higher TNs can be employed by the Game Master to represent harder or more difficult Tests. Each level of difficulty increases the TN by +3, with the highest being TN 34+ representing "Impossible" Tests.

An Average TN 7+ Tests has a 58% chance of passing whenever 2D, "two six-sided dice" are rolled. The "D" in "2D" represent the number of Base dice. 

Adjusting Success

During game-play, there will be Skills and Traits which award additional Base dice. One of the more significant ways is through the use of Favor dice.

• As a character progresses from mutation, their character level, known as PML or "piconit metastasis level" increases, their personhood becomes more aligned with the simulation that is the world of Sarna Len. 

• Each PML increase provides an additional Favor die. For example, a PML 3 (or "3rd level character") receives 3 Favor dice every game session.

• These Favor dice may be spent during any gaming session and are replenished to full at the start of the next session. Each Favor dice provides +1 Base die to be used for any Test.

It can be seen that even with 7D, presuming two standard Base dice, plus five more from Favor dice, that Impossible TN 34+ has about a 2% chance of passing.

Max Advantage

Sir Giles is PML 5. 

He receives 5 Favor dice, to spend as Base dice, during any gaming session. However, he can't spend them all at once because there is a Max Advantage limit equal to 1 plus a third of his PML for any Favor dice, dropping fractions. This makes his spending limit for any single Test become 2 Base dice beyond his normal 2.

The Max Advantage limit also affects how many Bonus dice are allowed beyond the standard limit of up to +2. Therefore, at PML 5 Sir Giles is allowed up to a total of 4 Base dice and 4 Bonus dice, after flattening.