Dicekind

The Fluorite Octet are an enchanted set of dice (or a set of enchanted dice), possessed by Vriska Serket.

History
Historically, dice weapons were employed by Gamblignants, a type of risk-prone Alternian marauders, who are now believed to be extinct.

The Fluorite Octet were discovered aboard a ghost ship by Vriska Serket during a difficult role-playing campaign - possibly a game of Flarp. 

Description
There are eight eight-sided dice in the set ("8d8" in pen-and-paper role-playing parlance), and they appear to be composed of one of the blue varieties of fluorite. The numbering is different from either traditional Earth dice or human role-playing dice, as each side has a unique pattern of pips, including a triangle of pips for three, a parallelogram for four, a sort of arrow-shape for five, a hexagon for six, and a pattern for seven resembling the design of whatever that thing was on Vriska's left eye before she lost her vision eightfold. The design for eight is identical to that for seven, with a single additional pip set to the side.

Use
They are used by rolling the full set. Each of the eight numbers in a roll is considered unique - the result of the roll is determined not by the total number rolled, but by the combination of numbers rolled by each die. Think of the result of a theoretical roll as being "65274318", for instance, not "36". It is not known whether the identity of each of the eight numbers is determined by the order in which the dice fall, or whether each die has a set place in the final permutation of numbers.

There are a total of 8 8 - or 16,777,216 - possible permutations of rolled values. The attacks resulting from these rolls are said to be "highly unpredictable", and fortunate results are "devastating to even the most powerful opponents." 

Known techniques include Musclebeast, Blizzard, Weasel, Levitation, Reroll x 2, Dutton, Naptime, and Guillotine. This consists of the set of results that can be determined by one die when the other seven are already set in their values - it still leaves unknown the results of the other sixteen million, seven hundred and seventy-seven thousand, two hundred and eight permutations. It is not known whether multiple different rolled permutations can result in the same attacks, though it is implied that there are a full field of results, numbering eight to the eighth power, with a unique attack for every possible roll.

The "Guillotine de la Marquise" technique was seen to summon a spectral blue guillotine, perfectly sized for the target, which then beheads the target.

The "Reroll x 2" technique presumably allows the user to roll the Octet two more times, and then presumably executes the attacks resulting from both rerolls.