Oath chess

You can, at a certain move by your opponent, prevent that your piece is taken by an enemy piece, by taking an oath, that from that move, your piece and all your pieces of the same type, will no longer be able to capture that enemy piece and all enemy pieces of that same type.

[added later]An oath with any combination of allied and foe piece type can only be taken once and won't protect against capture on a later move.
A King can't take an oath and therefore cannot be protected by it against check or mate.[/added later]

Example:

Black to move black wants to take a white Knight with a black Bishop. White can take an oath. During that move, Black cannot take that white Knight, and must play another move. But for the rest of the game, no white Knight can ever take any black Bishop.

In the position given above, that will allow white to fork the black King and Queen, and win the black Queen. But after the intended Nxa8, the white Knights are harmless against the black Bishops. So in this case, taking the oath may lose anyways.

Addition:

During any of your opponent's move you can only take an oath once. If the direct response to your oath is anothe capture then that other capture takes place anyways.

In this example, Black is not bound to any oath not to take white Knights with black Bishops during later moves.

Okay this is a neat variation ya like phone a friend. In millionaire

So to take an oath usually weakens your own pieces, so you won't do it unless there's a very strong immediate tactical advantage.

Do your worst ... Uh wait....promise variation

do promoted pieces count as pawns or the new piece

 Can the king take an oath

As the new piece

Yes

So how is it ever possible to conduct a checkmate? You can just swear an oath every move

You're right.

The King can't take an oath. Thanks for bringing this up.

1. Can you take an oath for a piece you're not moving? In the provided diagram, can Black, while moving his king out of check, protect his queen by taking an oath not to capture White's knights with his queen?
2. Can you swear multiple oaths on the same turn?
3. Can you swear an oath to the enemy king? If so, will the sworn piece type still be able to give check/checkmate, since that isn't technically a capture?
4. It seems only right that a player must swear an oath before he makes his move, so that the oath applies to his move. Is this accurate?

1. You swear the oath during your opponent's move, only when your opponent intends to capture one of your pieces, and then only for that piece type.

The procedure is:

- Your opponent captures your piece.

- You take an oath.

- Your opponent does another move (previous move is reverted and has not taken place)

- Now it's your move.

See previous post

The question is if during the opponent's move, the oath procedure can repeat itself when the opponent responds with another capture. The answer is no. If I allow it I foresee more situations that require additional rules and clarifications.

Yes you can. But that piece type becomes harmless to the King. A piece harmles to the King does not give check.

My general opinion about variant rules is: any piece that has no power to capture a King can also not give check.