Games of the Discworld

The fictional universe of the Discworld novels by Terry Pratchett features a number of invented games, some of which have gone on to spawn real-world variants.
Stealth chess is a chess variant, played in the Ankh-Morpork Assassins' Guild, according to The Discworld Companion.
It is similar to normal chess, with the exception of an extra piece and the widening of the board by two specially-colored fields (red and white are described, as opposed to the normal black and white) on either side, known as the Slurks. The extra piece is the assassin (appearing on either side of the rooks in the beginning of the game), the only piece to be able to move in the Slurk.
The assassin moves one square in any direction, and two to capture; however, on exiting the Slurks, the assassin may make as many moves as it has taken within the Slurks and, optionally, a capture move.
An example may clarify: If an assassin enters the Slurks and takes five moves within them (in any direction, including back and forth), it may then appear in any square that is five moves from its original entry point into the Slurk. It is then still able to make a one-square move to capture. If an assassin were to make fifteen moves (the minimum necessary to go from one corner of the normal board to the opposite corner), it could reappear anywhere on the board. The mechanism of moving the assassin up and down the Slurks is used in order to (a) use up a move by the player and (b) to keep count of how many spaces the assassin has moved.
The Slurks are, in essence, a second, "invisible" board, through which only the assassin may travel, and from which it may reemerge on the "visible" board at any time. The assassin may take pieces of its own colour, should this give the player an advantage, but may not take opposing assassins (professional courtesy). Many players consider the assassin to be moving "underneath" the actual board, ready to pop out when they have reached their intended destination.
This makes it a highly powerful piece and a very effective counter to certain strategies depending on specific pieces, and can quickly win the game if one manages to take control of the Slurks and access the king directly. The Discworld Companion notes that players should also take care that they do not focus on the opponent's assassin exclusively to the point that they lose track of what the opponent's other pieces are doing.
The acknowledged master of the game in the books is Lord Havelock Vetinari, Provost of Assassins and Patrician of Ankh-Morpork.
According to the Companion, some Discworld scholars believe that Stealth Chess is the original form of chess in their world; this belief is corroborated by the in-world discovery, in a tomb in Muntab, of a preserved corpse with an 8×10 board embedded in its skull and a pawn hammered up each nostril.
Cripple Mr. Onion was originally a fictional card game played by characters in the novels Wyrd Sisters, Reaper Man, Witches Abroad, Men at Arms, Wintersmith and Lords and Ladies. A game called "Shibo Yangcong-San" (derived from Japanese 死亡 shibō, "death;" Chinese 洋蔥 yángcōng, "onion;" and the Japanese honorific さん -san) appears in Interesting Times as a tile game played in the Agatean Empire. This was used by Dr Andrew Millard and Prof. Terry Tao as the basis for an actual card game. The complete rules and design of this game were posted on Usenet around 1993 and were approved by Pratchett himself. It contains elements of blackjack and poker.
The game requires an eight-suited card deck, with suits representing the eight Minor Arcana suits of a Discworld Tarot, or "Caroc" deck: the staves, swords, cups, and coins of real-world Tarot plus four additional suits named for octograms, elephants, terrapins and crowns. For the purposes of flushes, each of the real-world suits is paired with one of the four Discworld suits (a commercially available deck marketed for use in the game includes axes, tridents, roses and doves as suits to be paired, respectively, with the more traditional clubs, spades, hearts and diamonds). For real-world play, two distinctive but identically-backed "normal" decks are generally used, most frequently a traditional "French" deck and an identically-backed Latin-suited deck.
Each player receives a hand of ten cards: five cards are dealt face-down to each player, and the player may then discard up to four of them, receiving new cards to replace them. Then a further five cards are dealt face-up to each player except the dealer, who receives his face-down. The first player begins by assembling their cards into one of the winning groupings described below, and displaying them. The next player must then create a more valuable grouping or fold. If the player is successful in creating a more valuable grouping, the original first player may try again to create an even more valuable grouping for themselves, or fold. This process passes left around the table until only one player remains, who then wins the hand.
The categories of winning group, in ascending order of value, are as follows. Number cards are worth their face value, picture cards are worth ten, and aces are worth one or eleven at the player's choice (as in Blackjack).
"Modifiers" may also be played to increase the value of a hand. Apart from the crippling rule, modifiers are optional rules, which may or may not be included in a game. The available modifiers (many of which are named after Discworld characters or concepts) are as follows:
Running flush: The cards form an unbroken numeric sequence and are either all the same suit "n card Running Flush" or all but one are of the same suit "n card Running Broken Flush. This is the same as a Straight Flush in poker.
Thud is a board game devised by Trevor Truran and first published in 2002, inspired by the Discworld novels rather than originating in them. It bears a strong resemblance to the ancient Norse games of Hnefatafl and Tablut but has been changed to be less one-sided. The two sides are dwarfs and trolls.
In the game, the objective is to eliminate as many of the opposition's pieces as possible. The two antagonists are the trolls and the dwarfs, the trolls being few in number (but individually very powerful), while there are a large number of dwarfs, but each individual dwarf is very weak and requires support from nearby dwarfs to be of use against the trolls. As in fox games, the two sides have different pieces with different movement and attacking styles.
Thud uses an unconventional, octagonal board divided into smaller squares. However, in the televisual adaptation of Going Postal, a Thud board was depicted as resembling a typical square chessboard.
The game, supposedly called in Dwarfish "Hnaflbaflwhiflsnifltafl" (a reference to the Viking game Hnefatafl which it resembles), represents the famous "Battle of Koom Valley" between dwarfs and trolls.
The game was first directly referenced in Going Postal, being played by Vetinari, and was a central concept in the following novel Thud!, whose plot was inspired by the game. The release of Thud! in 2005 led to a special Koom Valley edition of the game published by Mongoose Games and featuring a new "Koom Valley" variant inspired by the plot of the novel (see below), and using the book's cover artwork, drawn by Paul Kidby. A third edition, featuring a cloth board and carry bag, was published in 2009.
Terry Pratchett devised a fictional history of how Thud was invented similar to the Shahnama theory of the origins of chess. In short, the clever dwarf who invented the game was asked by his king to name his reward. The answer was that he wanted his board filled with gold: one small gold piece on the first square, two pieces on the second, four pieces on the third and so on. Upon realising this would equate to more than all the gold on the Disc, the king got angry and threatened to kill the dwarf who was "too drhg'hgin clever by half". The inventor then hastily changed his reward to 'as much gold as he could carry', to which the king agreed before breaking one of his arms.
This story appears in all three editions of the game, and also appears in the collections Once More* with Footnotes (as "The Story of Thud") and A Blink of the Screen (under its original title, "Thud: A Historical Perspective").
The octagonal playing area consists of a 15 by 15 square board from which a triangle of 5 squares in each corner has been removed. The Thudstone is placed on the centre square of the board, where it remains for the entire game and may not be moved onto or through. The eight trolls are placed onto the eight squares adjacent to the Thudstone and the thirty-two dwarfs are placed so as to occupy all the perimeter spaces except for the four in the same horizontal or vertical line as the Thudstone. One player takes control of the dwarfs, the other controls the trolls. The dwarfs move first.
On the dwarfs' turn, they may either move or hurl one dwarf:
On the trolls' turn, they may either move or shove one troll:
The battle is over when both players agree that no more captures can be made by continuing to play, or when one player has no more valid moves to make. At this point the players count score: the dwarfs score 1 point for each surviving dwarf, and the trolls score 4 for each remaining troll, with the difference being the 'final' score. The players should then swap sides to play another round, and the sum of their final scores for the two battles determines the overall victor.
The basic overall strategy is for the dwarfs to form a large group and for the trolls to try to stop them.
A dwarf's strategy does widely depend on how the trolls are advancing on the dwarf block. A good tactic therefore is to be prepared to sacrifice a few dwarfs to get in the way and slow down any trolls that are advancing into dangerous positions.
For the 2005 rerelease of Thud, Truran devised a substantially different game that could be played with the same board and pieces, known as Koom Valley Thud. Unlike the original release, in which the publishers attempted to keep the game rules secret so that anyone wishing to play would have to buy the official set, the rules for Koom Valley Thud were posted on the official website so that owners of the original edition would have access to the new rules.
There are only sixteen dwarfs in Koom Valley Thud. Fifteen are placed so as to fill two diagonal sides of the board and the orthogonal side between them. The sixteenth is placed next to the Thudstone, called the Rock in this variant, on the dwarfs' side. The eight trolls are arranged in a symmetrical pattern in three groups on the other side.
For the dwarfs to win, they must move the rock to the far side of the valley – onto any of the five squares on the opposite side of the board against which the dwarf player is sitting. For the trolls to win, they must capture the rock by placing three trolls adjacent to it (in any direction including diagonally). If neither side can achieve their objective, the game is drawn.
Movement is the same as Classic Thud except that trolls may now move up to 3 spaces in any direction (horizontal, vertical or diagonal).
Dwarfs may move the Rock instead of moving a dwarf piece. It may move only one square in any direction. To be moved it must be next to a dwarf and it must also be next to a dwarf at the end of its move.
A troll captures a dwarf by trampling over it. It moves in a straight line from a square next to the dwarf, through the square the dwarf is on and lands on the empty square immediately beyond. The trampled dwarf is removed from the board.
Several captures may be made in one move and a change of direction is allowed between captures.
Dwarfs capture a troll by moving a dwarf so that the troll is trapped between two dwarfs in any straight line (including diagonally). The three pieces, two dwarfs and a troll, must all be in line.
If the dwarf that has been moved also traps another troll between itself and another dwarf, that troll is also captured.
Captures are only made when the capturing side moves a piece. The rock may be moved and come to rest next to three trolls. It can only be captured when a troll is moved.