Index -> Playing the Game -> Execution Phase -> Destiny Phase
In this phase, each planet a player controls gives him a number of destiny points equal to its current culture value. If a planet is blockaded, it gets only half that number of destiny points, rounded down.
Destiny represents the cultural accomplishments of your race. If you fall behind any of your opponents in accumulating destiny, you will see a negative destiny number displayed beneath your name at the top of the map. This indicates how many points you have fallen behind the destiny leader.
Typically, only artifact planets have culture to generate destiny, as they contain ruins left behind by the Atok, the ancient race that built the interstellar gateways. Each artifact planet has a base culture value of 2.