Filena

Filena is a secondary character in Quantum Theory and Syd's partner. She is voiced by Megan Hollingshead and is playable in multiplayer matches.

Role in Game
An enigmatic figure seen fighting the Nosferatu and Gillskins, Filena's goal is to locate her father, the creator of the Tower. She is initially distrustful of Syd, though holds off from attacking him until he tries breaking one of the lumenosynthetic reactors. Upon failing to stop his rampage, she realizes the destruction of the reactor stopped the Diablosis from spreading briefly.

Although she and Syd are technically enemies due to being Nosferatu and Gillskin respectively, they agree to form a truce in order to learn the truth behind the Tower's existence. While maintaining her origins as a human and dismissing Syd's doubts, she slowly opens up to him as they defeat their foes side by side.

Much to her surprise, Filena learns she is an artificial humanoid engineered by her father to perfect life. She also becomes a target by the invading Gillskins to bolster the effects of the Diablosis. While she ends up being absorbed by Thanatos during the conflict, Syd finishes it off and frees her.

The pair head to the top floor where the Seed instructs Filena to shoot Syd. She seemingly aims her gun at him, but ends up firing at the Seed in defiance of its grand design. Confounded by Filena's apparent free will, it desperately tries to placate her as the Tower begins to crumble. While Syd assumed the Tower's collapse would mean her demise, she subverts his expectations by escaping alongside him. Both are later seen heading for another Tower after the credits roll.

Gameplay
As the player's partner, Filena's actions are mostly controlled by the AI. Her weapon functions as a sword and pistol, providing more versatility in numerous situations. When together with Syd, the two of them can perform a wide range of combos.

Holding L2 allows Syd to toss Filena towards the target from a distance and strike them down directly. Simply tapping it will make her leap up and toss needles that briefly paralyze enemies below. These attacks are available so long as the player's gauge turns blue.

Melee combos between Syd and Filena consist of the following button inputs. These are activated once the gauge flashes.
 * First Hit: or undefined - A simple strike.
 * Second Hit:, - Launches a crowd-clearing attack.
 * Alternate Second Hit: undefined - Inflicts heavy damage against a single enemy.
 * Third Hit:, or undefined,  - Delivers several swift kicks that scatter nearby enemies.
 * Alternate Third Hit:, or undefined,  - Does severe damage to one enemy, though the hit frame for this attack is low.