Fairy retros are retros with fairy chessmen
Many have been composed. The motivations for introducing fairy pieces
and/or conditions in retros are exactly as for usual forward
It is quite straightforward to understand how fairy conditions can
be incorporated in retros once you see that all retro-stipulations can
be rephrased in terms of the existence of legal proof games with given
peculiarities. Then, assuming a given fairy condition, you just have
to know what is a legal proof game.
This is no problem in many cases where you just play the "usual" fairy
moves starting from the usual starting position. This applies e.g. to
Circe chess, Monochromatic
chess, chess on a grid-board , or on a
Some other fairy conditions needs explicit stipulations when the implicit
starting position will not do. But there are some default rules: most
used is the following rule "when fairy men appear on the diagram,
it is assumed that they did not exist in the starting position but that
promotions in these fairy men are allowed".
Sometimes, the stipulation says that the fairy men replace
(some of) the usual men: e.g. Maos or
Nightriders instead of Knights. (This situation
is more properly seen as a fairy condition because it assumes that the
usual Knights do not exist anymore: you can't promote in Knight, ...)
Observe that in some retraction problems
with a stipulation of the form "White retracts his last move and
then mate in one" the legality of the position is not really at
stake, and the only question is to find the hidden tricky retraction
move that will allow a mate in one. These problems will accomodate fairy
men on e.g. an horizontal cylinder without requiring specific explanations
about how the game really started.
The retro-glossary has entries for a few fairy conditions / fairy
men, most of them with actual examples of how they can be used to achieve
specific effects in retros. Look
at them! I also started to collect some fairy retros on
a page of their own.
It is instructive to reflect on the fact that many of the most popular
fairy rules used in retros mostly restrict the list of legal moves in
a given position. These constraints on valid proof games let the composer
enforce additional maneuvers in the retro-play without requiring the
many apparent scars that are customary.