The Mandarin-the Entity chess match

The Entity, challenged to a game by the Mandarin in his non-world, chose a game of four dimensional chess.

Origins
The Mandarin wanted to challenge the Entity — or Aboo-Fenran as he was then known — to a game while he stalked the Arabian plains, but was unable to do so as the Entity (PROSE: ) was imprisoned in the Shadow Dimensions by the Seventh Doctor. (TV:, PROSE: ) So, the Mandarin had to travel to the non-world where the Entity resided to challenge him. (PROSE: )

The game
After settling the stakes — if the Mandarin lost, he would relinquish his body to the Entity, or, if the Entity lost, he would become the Mandarin's toy — the Entity, as the one challenged, selected four dimensional chess as the game of choice.

The board, a large translucent sphere, grew from a "tiny" light, and the game began. The sphere began rotating, the board pattern changing over the course of the opening gambit resulting in the "structure of the conflict" rearranging multiple times. The duo played at lightning-fast speed, pieces seemingly disappearing and reappearing, other moves from the future "twist[ing] back on themselves" to affect moves in the present, with the advantage shifting between the adversaries.

During the middle of the game, three of the Entity's Kings fell. The game progressed over an unknowable duration of time — perhaps a nanosecond, a day, or a year — but the endgame eventually neared, and the Mandarin realised, for however much of a "magnificent gambit" the game had been, he was losing; his "position was poor, his forces weak."

Preferring not to lose, a concept foreign to him entered his mind — a stalemate — and so he consolidated his pieces, resulting in the Entity not being able to penetrate the Mandarin's defences without scattering his own pieces. Thus, a stalemate was reached. (PROSE: )

Aftermath
While the Entity demanded a rematch, the Mandarin declined, stating that the result would remain the same as they were too equally matched. The Mandarin thanked the Entity for teaching him a "valuable lesson", that "perhaps winning [wasn't] everything", and left the Entity's domain, with the words that the Mandarin spoke remaining with the Entity long after. (PROSE: )