Knight Relay chess (also called N-Relay chess) is a chess variant invented by Mannis Charosh in 1972. In this game knights "relay" their power to friendly pieces.
Any piece, except for the king, which is defended by a friendly knight gains the power of a knight. The piece loses the additional power as soon as a friendly knight no longer defends it. Knights are immune from capture, cannot capture enemy pieces and (so) cannot give check. Pawns may not move to the first or last rank by a relayed knight move. If a pawn is relayed to its initial rank, it regains the option to make a double-step move. There is no en passant in Knight Relay chess. Pawns can promote to knights and promoted knights also have relay power.
The diagram shows possible moves of the white pawn on e6. As a normal pawn it can move to e7 or capture on d7 or f7. In addition, since it is defended by a friendly knight on d4, it can move like a knight to c7, c5, f4, g5 or g7. It cannot relay as a knight to the last rank, and the black king on d8 is not in check. The white knight on b7 does not check the king either, and is not able to capture the pawn on a5. The white queen cannot take the black knight on c3.
White can deliver checkmate in this position by playing Qd6#. The black king cannot escape to c8 or e8, since those squares are attacked by the queen on d6 (the queen getting knight power from the knight on b7).