Supertransmuting King (Pressburger King): When checked, a king must play as the unit or units giving check if possible, thereafter the king becomes an ordinary (non-royal unit) of this type permanently. If it is not possible to move as the checking unit, another piece may parry the check and the king does not change. If that is not possible, the king is mated. (Stephen Emmerson, A Glossary of Fairy Definitions, BRITISH CHESS PROBLEM SOCIETY, July 2018)

Grasshopper (G): Moves along Q-lines over another unit of either color to the square immediately beyond that unit. A capture may be made on arrival, but the hurdle is not affected.

Royal piece: Piece that executes a function of the King on the board. Subject to check, in the same manner as the king in normal chess. As is the case for kings, if a royal unit is checked, the check must be annulled immediately, and if this is not possible, the side to which the royal unit belongs is mated.(Royal pawns promote to royal pieces.)