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This page is written by the game's inventor, BryanLambert.

Poison Chess


In the game Jupiter, I saw a reference to the ability for some pieces to "poison" another piece. I have used that idea in this variant, but not in the same fashion.

I began drawing up the details of this game around June 14, 1999.

Additional Equipment

You will need one checker for each opponent to represent a poisoned piece (place the checker under a piece after using the poison). Some other checkers might be useful as a countdown (5, 4, 3...).

If you have another spare chess set, I suggest setting aside a Rook or a Queen (Guard) in case of pawn promotion. (Of course, you may not need them at all...)


Similar to FIDE Chess, but with a few changes (read below).

Board Setup

The board is a regular 8X8 checkered board, where there are two new pieces: the Harpy (H, h) and the Doctor (D, d).

The setup is exactly the same as orthodox chess (King on opposite colour, lower-right square white, etc.) with the Rooks replaced by the Harpies, and the Queen replaced by a Doctor. The Queen is absent from the game. Thus, the board looks like this:

King e1; Doctor d1; Harpies a1, h1; Bishops c1, f1; Knights b1, g1; Pawns a2, b2, c2, d2, e2, f2, g2, h2.

King e8; Doctor d8; Harpies a8, h8; Bishops c8, f8; Knights b8, g8; Pawns a7, b7, c7, d7, e7, f7, g7, h7.

The object of the game is to checkmate the enemy King. You can also poison the enemy King with a Harpy. You then win if your opponent does not get his Doctor (if alive) to his King in time. (Of course, if one has lost his Doctor, a Poisoning would be deadly.)

Piece Movement

The King, Bishop, and Knight are as in regular chess.

The Harpy, while bearing the name of a piece that moves like a Queen in Jupiter, only moves here like the Rook in orthodox chess (hence its starting location). It can capture other Harpies, but cannot capture any other pieces; however, it has the special ability to poison a piece instead of moving. A Harpy can poison any enemy piece, including the opposing King, in the eight squares surrounding it. When the Harpy uses its poison, it is removed from the board (it can only poison once). If the Harpy is captured before using its poison, the piece that captures it does not become poisoned.
The poison is in effect for 5 moves (much like the trapdoors in Trapdoor Chess). If the poisoned piece is still poisoned after 5 moves, it is removed from the board. If captured, the poison does not transfer from the poisoned piece to the capturing piece; instead, it has no effect (but wastes the poison).
Since, in reality, a person who is poisoned is usually expected to remain bedridden for a while, I decided to freeze a poisoned piece on its square, unable to move, for the duration of its poisoning. This brings in new mating possibilities, and alleviates others; see below.

The Doctor is designed to alleviate the poison injected by the Harpy. The Doctor moves and captures like the orthodox Queen. The procedure for curing a piece (within the eight squares surrounding a Doctor) is similar to the poisoning of a piece in that it occupies one turn; however, the Doctor remains on the board and continues moving and capturing as normal. (The curing procedure CANNOT be used on unpoisoned pieces to "skip" a turn.)

NOTE: Doctors CAN be poisoned! A poisoned Doctor must then spend a move healing itself, or let the army continue its carnage and die instead.

Pawns move as normal, with the two-step option on the first move. En passent is possible. Pawns can promote to Knight, Bishop, Rook, or Guard, which moves like a Queen and can be represented by G (g).
This latter promotion addresses one thing I've always found strange in chess: how could a male pawn become a female Queen? (By a very quick operation in a fictitious hospital stationed on the promotion square, right?) ;-) Therefore, I will not allow a sex change to take place in my variants. However, regardless of the Guard's roles in other variants (if any), I give the Guard the ability to move as a Queen to compensate for the missing Queen promotion.
I decided, after some thought, to allow the Pawn to promote to the Rook, even though it is not present at the start of the game. Why? Well...there's a Guard replacing a Queen promotion, so why not? ;-)
Note that a Pawn cannot become a Harpy or a Doctor, as a soldier cannot simply grow a stinger and years of medical training are required to become a Doctor.

Check and Checkmate

A King is in check when it is attacked by an enemy piece. He is NOT in check when threatened by a Harpy (though, if the King falls to the poison, the game ends immediately). If the check cannot be alleviated, the game is won for the checking player.

If a King is poisoned, he is frozen just like any other piece and a Doctor must rush to the scene. If the King is placed in check while poisoned, the King cannot move; instead, another piece must interpose or capture the checking piece. (Otherwise...checkmate!)

It is important to note that a poisoned piece does NOT give check until it is cured. This is handy when your King is cornered; you can poison a trapping piece, move the King as is newly able, and continue play. (Note: in the case that one King is poisoned, the two Kings CAN stand next to one another, in which case the non-poisoned King is the winner because he captures on the next move. However, if this capture puts the non-poisoned King into check, it is illegal and the Kings must soon split if the other King is cured.)


Since the Harpy moves like a Rook, I decided to permit an unmoved King and Harpy to castle as in ordinary chess. The King moves two squares towards the Harpy, and the latter moves to the other side of the King. The restrictions regarding check are the same.


If a player's King is poisoned and he has no other legal move, the game is drawn. Since a poisoned piece cannot move, having a couple of Harpies and a King versus a lone King is pretty ridiculous.

If a King is poisoned with no Doctor to save him, the King's owner can still play for checkmate. If he achieves checkmate within the five moves (still taking turns), the game is a draw.

Other conditions for drawing (50-move rule, etc.) apply as in orthodox chess.


I kept the conventional notation, but added square brackets to represent poisoned pieces. So:

If any readers have ideas on how to improve the notation, don't hesitate to write me. I'm very receptive to new ideas.


I present to you a problem to solve. White mates in two moves.

King g1; Doctor e3; Harpie e5; Bishop h4; Knight h7; Pawns a3, b2, c4, f2, g2, h3.

King e8; Doctor c8; Harpie a6; Bishop a5; Knight f5; Pawns a7, b6, d7, f7, g6, h6.

Black just played 1. ... Nf5??, forking the Doctor and the Bishop, but allowing mate in one. What is White's winning move?

Naturally, I'd like you, the user, to try this puzzle before I tell the answer.

If you're stuck, try placing the King in check.

If you still don't know, try poisoning a piece.

If you're still without an answer, I must now tell you what it is. The answer is 2. xHe5#[f5,5]. This poisons the Knight on f5, rendering it immobile. It is unable to capture the Doctor and is unable to interpose. Ironically, there are no other pieces that can defend the check, and there are no safe spots for the King, so...checkmate!

Notice, if White plays any other Harpy move (like 2. Hc5), Black simply captures the Doctor with the Knight. Keep the above strategy in mind!


It is important to remember that Harpies cannot capture, only poison. Keeping pawns in front of a castled King is essential, but leave a tiny space on the side by moving a pawn up so the King can avoid the Harpy (or another check) on the back rank.

If your opponent unwittingly poisons a pawn, don't bother curing it unless it's a promotion possibility. No sense in wasting time fussing over a footman stuck on his starting square!

Keeping a Doctor near your King is sometimes a good idea. When the King is threatened by a Harpy, the Doctor can capture the Harpy. Otherwise, the Doctor must waste turns running to the King...

Keeping friendly poison near a King is also good; you can poison a piece positioned near the King. Remember, the poisoned piece does not give check!

Here's something that a Harpy user MUST remember: upon poisoning an opposing King, in order to prevent the opposing Doctor from reaching the King, you should constantly put the opposing King in check however you can. If you keep your opponent at bay for five moves, you are the winner!

I said, above, that Doctors can be poisoned. This is, of course, extremely worthless unless such a move gives check at the same time (a discovered attack that had been blocked by the Harpy). The check should then be followed up by an attack on the Doctor, who cannot capture the attacker himself.

There are other strategies that will no doubt be developed over time, and they'll be posted here. The possibilities are almost endless with this game.


I think a good way to remember a poisoned piece is to use checkers to represent such pieces. If you want to simulate a countdown, the best method is by placing five checkers under a newly-poisoned piece, and removing one for each opponent's turn. If a piece runs out of checkers, it's dead. If it's cured, simply remove the checkers and continue using the piece.

On an ASCII diagram, you can place numbers around a poisoned piece to represent how much time remains. So, 4B4 | is a Bishop with four opposing moves before death, and 1N1 is an almost dead Knight.

My original idea for this variant was a 10X10 board with a normal setup flanked by two extra columns holding Doctors and Pawns. Harpies would replace the Rooks. I decided to keep things simpler than that. However, my former idea works as a large variant (though, of course, the Doctor should move differently...).

If you would like to add any comments regarding notation, strategy, or otherwise, or would like to suggest a variant of this idea, you are encouraged to contact me at by email (the email address can be found by clicking the link with the name `Bryan Lambert' at the bottom of this webpage; editor). If I like your suggestion, I may implement it.

If you try this game out with a friend, let me know how it goes. Feel free to write out the game (read the Notation section carefully) and send it to me via E-mail.

Comment regarding "Zillions of Games"

I don't currently own the software, so I cannot actually playtest the games I invent. I have to try my luck at improv...

Anyway, my previous variant, Bomberman Chess, spawned a Zillions implementation about a month and a half later. I'm OK with this, though I've never seen it. (Compare it to the given rules and let me know how it works, if you download it yourself.) Fortunately, I had played two sample games (one with a friend), so I had clear rules present.

My original idea of Poison Chess seemed kind of challenging even for Zillions of Games, from what I've seen. (This new one may be workable.) If anyone plans to create a Zillions implementation, please let me know by email. (Click the name `Bryan Lambert' below to get the most current email address; editor.) and I'll clarify any vague rules (and change them here). If you plan to do an implementation, please let me know! (BTW, I know nothing about the program (yet), but I hope to get it soon, possibly in September if I have the money and a Windows-capable machine [like a G3-Mac?]. Too much chess fun I'd be missing otherwise!)

Sample Game

I plan to try out this game with someone. I will record the game, if I get to play it. The game will then be posted on this page as a sample.

Written by: Bryan Lambert. Editor comment added by Hans Bodlaender.
WWW page created: June 14, 1999. Last modified: September 27. 2002.