String Theory: Aftermath allows players to have 5 characters: 2 SLC-Expressive, 2 Non-Expressive, and 1 "Fusion Character" character (FC) who may possess more than one SLC-Expressive ability.
If you do not currently have a FC, or are retiring your current FC, you may promote one of your pre-existing characters to FC status.
Retiring and Rotating Characters
Sometimes a character needs to be retired or rotated out to allow their story to simmer in the background, allowing the player to take on another new character.
If you are retiring a character, you must place a +request indicating what character is being retired and (in estimate) for how long. Once a character is retired, that character's slot is open (Evolved, Non-Evolved, or FC) and you are free to make a new character.
If you are bringing a retired character back, you must also +request the character's return and have an appropriate character slot available.
In Aftermath, when you retire a FC, they are usually retired permanently. This prevents players from cycling through Fusion Characters. How this takes shape is decided by agreement between staff and the player.