endgame

Short definition from Wiktionary

Noun

1. 1
   The final stage of a game of chess, when there are few pieces left.
2. 2
   The final stage of a game of bridge, when there are few cards left.
3. 3
   The final stage of any game.
4. 4
   The final stage of an extended process or course of events, especially with the implication of the imminent realization of a masterful strategy or plan.
5. 5
   The gameplay available in a massively multiplayer online role-playing game for players who have completed all of the preset challenges.
6. 6
   The thematic element of an advanced cryptic crossword puzzle, typically solved after completing the grid.

Adjective

1. 1
   Having become canon by the end of the plot of a work of fiction or speculated to be intended to become such.