Indroduce new Piece on board

[govind-maheshwari2]

I want to add new type of piece on board other than P,N,B,R,Q,K. I want to introduce S. It will be static on board opponent pieces can capture S but S can't move to capture anyone.

[alexobviously]

Well that's an easy one! You just need PieceType.fromBetza('') (actually you could do it with the basic constructor but for a number of reasons I recommend sticking with fromBetza). You probably also don't want to promote to this piece I guess.

So your variant probably looks something like this:

final govindChess = Variant.standard().withPieces({
    'S': PieceType.fromBetza('', promoOptions: PiecePromoOptions.none),
  }).copyWith(
    name: 'Your Variant Name',
    startPosition:
        'rnbqkbnr/pppppppp/8/2ssss2/2SSSS2/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1',
  );

Just included the start position as an example to show you how to do it.
Another thing you might want is to set materialConditions: MaterialConditions.none - this will prevent a draw from being called on insufficient material, because your new piece probably changes the logic for that.