fbNFR == worth a Queen.
The Fibnif is worth a piece, so adding a Rook to it should make a new Queen. Although this is probably a weak Queen (it might be a third of a Pawn weaker than the FIDE Queen), picture a position with a White fbNFR on e6 and a Black King on e8.
Gosh, that's checkmate! In fact, fbNFR can force mate without help of its own King.