The phrase "as an optional character" is correct and usable in written English.
It can be used in contexts where you are discussing elements that can be included or excluded, such as in programming or writing specifications.
Example: "In the password requirements, you may include special symbols as an optional character to enhance security."
Alternatives: "as an additional character" or "as a non-mandatory character".
Aside from his appearance in the XIII games, the character was featured in the rhythm game Theatrhythm Final Fantasy as a subcharacter representing Final Fantasy XIII, and his outfit from that game was featured as an optional character costume in Final Fantasy XIV: A Realm Reborn along with Lightning's Guardian Corps uniform.
There are seven party members in total: Goombella the Goomba, Koops the Koopa, Madame Flurrie the spirit, a Yoshi (named by the player), Vivian the Shadow Siren, Admiral Bobbery the Bob-omb, and Ms. Mowz, who is available as an optional character.
Amos is an optional character, as it is possible to do his side story wrong & lose access to him forever.
With the chief source for his portrayal as one of the most active warriors of the Trojan War undermined, Troilus has become an optional character in modern Trojan fiction except for those which choose to retell the love story itself.
While in the first two titles he only assists X during gameplay, he becomes an optional character in X3.
She is an optional character, & her job class is automatically set to Dragon without needing the special item.
During character creation, the game had an optional character biography with unique positive and negative characteristics (increasing one ability while limiting another).
Our model extends the PWM model by introducing an optional character (or gap-character) to model variable-length motifs.
A redesigned Sephiroth also appears in the North American and European versions of Kingdom Hearts as an optional boss character in Olympus Coliseum.
As a result, Vincent and Yuffie ultimately appeared as optional characters in the game.
Dogmeat was introduced as an optional companion to the player character in the original Fallout (1997), and has also made cameo appearances in the sequel Fallout 2 (1998) and in some other video games.
