destroy the tower along with the erosion. The entire squad Syd is with is wiped out but he manages to enter the tower. Syd meets Filena for the first time when he sees her fighting the Nosferatu and comes to her aid. After dispatching the enemy the two engage in a Mexican stand-off, after which they go their separate ways in the tower. Filena and Syd meet again later on and reveal to each other their opposing quests: Syd is out to destroy the tower while Filena wants to save it from the erosion. The two battle to a stalemate as their fight is interrupted by the Diablosis, whom they must fight together in order to survive. The two agree to join forces for the time being. Filena tells Syd that her father created the tower, while throughout the story a voice speaks through the loud speaker in the tower, providing context. Later in the game flashback levels show Syd as a rookie, donning a mask which is broken in a later flashback, resulting in the x-shaped scar on Syd's forehead. During this time he was part of a squad of exiled Gilskins, the leader carrying the Revenant weapon Syd now uses. The entire squad is wiped out during a battle with Diablosis, only Syd survives, now using the leader's Revenant. Syd and Filena belong to warring factions, the Gilskins and the Nosferatu, respectively. Syd and Filena join together, but split up later on. Syd and Filena meet up again, and Filena discovers that she is not human, but the prototype of a new breed of humanoids that her father had engineered. She is also the missing component that would empower the Diablosis as they merge with the erosion. Syd and Filena battle the main Diablosis, but the Diablosis eventually absorbs Filena. Syd kills it and frees Filena. Filena and Syd make their way up to the top floor of the tower before confronting the brain of the tower, which instructs Filena to kill Syd. Filena points her weapon at Syd only to change her mind at the last second and open fire on the brain. This causes the entire tower to be destroyed. After the credits both Syd and Filena are seen going towards another tower. Reception Quantum Theory received mostly negative reviews, with a Metacritic aggregate score of 37/100 for the Xbox 360 version and 43/100 for the