Partial Paralysis: If the piece X is attacked by the piece Y then X cannot move as Y.

Leffie: A move is illegal if it leaves a piece paralysed in Eiffel. (introduced in Quartz 46)

Eiffel Chess: Units, other than Kings, are paralysed when they attack each other. The paralysis occurs in the sequence P-N-B-R-Q-P. A Pawn paralyses an enemy Knight; a Knight paralyses an enemy Bishop, and so on. A paralyzed unit loses all powers except that of causing paralysis. Fairy pieces play normal, without paralysis.

Neutral piece: Belongs to whichever side chooses to use it. It can therefore be moved or captured by White or Black, and in Circe it is reborn according to capture. A King may not be moved onto a square controlled by a neutral piece, because of self-check.