Each PC of level 6-10 has a Destiny. Destinies represent the ultimate goals, cosmic fate, accumulation of skills and experience, and even divine manipulations relative to the character. Prior to level 6, the character instead had a Background, as their backstory is still of primary importance in informing their general capabilities. Upon reaching level 6, the character abandons their Background in favor of a Destiny, as where they are going has become much more relevant than where they came from.
Each Destiny consists of a set of base Stat Track modifiers, effect text, and an exploration Action. Stat Track modifiers apply to all three scenario types. The effect text consists of various bonuses (and occasionally penalties) that may apply to one or more scenario types. The Action entry ensures that a player is always able to attempt to make progress against an Obstacle regardless of Gear or cards in hand. Compared to similar Backgrounds, Destinies offer better Stat Track allocations, stronger abilities, and superior Action dice.
Once selected, a Destiny can usually only be changed through extraordinary means. A transformation this significant may well involve beings of great power and/or sequences of events that drastically alter the direction a character has been heading their whole life. Such changes should be coordinated between the player and the DM and may involve a number of play sessions to complete. In certain cases the DM may agree that a different Destiny better suits the character as they have developed (particularly as new Destinies are made available for use), and some rare effects may allow changing of Destinies through other means.
A character that reaches level 6 does not somehow forget or rebuke their history because they no longer have the Background. The Background may be remembered in cases such as where the DM uses it to determine narrative knowledge and skills a character might possess beyond those represented in the mechanics. However, in most cases, adventure content at levels 6 and higher go well beyond such mundane ability sets, and it's knowledge and skills relative to the Destiny that should be more frequently considered.