Copyright (c) ~1780 Adam Vaugeois?
Queen's Guard (a.k.a. Agon) is played on an hexagonal board with the following setup:
- RING - Two cells belong to the same ring, if they are equally distant to the center cell.
- MOVE - The Guards and the Queen may move to any adjacent empty cell, with the following restriction:
- The move may be sideways, i.e., in the same ring around the center, or,
- The move may be into a cell inside the next inner ring, i.e., towards the center.
- A Guard may never enter the center.
- TRAP - If a piece moves to a cell, where there is an enemy piece between it and a friendly one (and all 3 pieces are in the same ring), the enemy piece is trapped.
- A trapped piece must, on the next move, be placed on any empty cell in the next outer ring (so, trapping a piece is like gaining an extra move, since the adversary must waste his next move to release the trap).
- If a piece moves between two enemy pieces, it also gets trapped.
- If the Queen and a Guard are trapped at the same time, then the Queen must be moved first.
- GOAL - Wins the player that places his Queen in the center, surrounded by his six Guards.
- A player looses, if his Guards are positioned immediately around the cell, and this is empty.
My impression is that the game is too drawish. One thing that may help is to modify the trap rule, and a trapped stone should be placed on the outer ring of the board, so in this way, trapping is a lot more stronger. But I think this is not enough...
Black's move. If Black could move to cell  it would win. But since it is trapped between two black Guards, it must go retreat to the next outer ring.
Concerning my last sentence, Damian Walker sent me the following comment:
You mention in your page on Agon, or Queen's Guard, that "One thing that may help is to modify the trap rule, and a trapped stone should be placed on the outer ring of the board, so in this way, trapping is a lot more stronger."
I have R C Bell's book Board and Table Games from Many Civilizations, and Parlett's book The Oxford History of Board Games, and both books say that this is how the game is played anyway. The exception is that when a queen is trapped, she may be placed anywhere.
They also propose a variant, though each is slightly different. Bell proposes that the queens start in opposite corners as in the normal game, but that the game starts with a placement phase, where players take turns to place their guards, one at a time, in any hex on the board (the centre excepted, presumably). Once this is done, play continues as normal. Parlett suggests that the queens are also placed, before the guards, in the same way.
There is a ZRF to play Queen's Guard with Zillions.