Desdemona is an Othello variant.
 
Othello rules: Black and White alternate putting disks on vacant squares from an initial opening position. Each disk must be placed so that it sandwiches one or more enemy disks between itself and another friendly disk, with no empty squares intervening. The sandwiched enemy disks are flipped, changing color.
 
If one player can't move, he must pass his turn. The game ends when neither side can move, usually when the whole board is filled. The winner is the player with the most pieces of his color.
 
Desdemona Rules: There is an extra stone, the grey one. When a player flips an enemy stone, it becomes grey. If a player flips a grey stone, it becomes one of his own stones.