Also known as the T-00 Tyrant, part of a series of intelligent bioweapons developed by the Umbrella Corporation, Mr. X pursues protagonists Leon S. Kennedy and Claire Redfield for a large portion of the game.

To the surprise of the game's developers, the remake's Mr. X gained "breakout" popularity amongst fans and critics, becoming an Internet meme due to his fear-inspiring implacability and incongruously gentlemanly appearance.

The Tyrants are bioengineered supersoldiers created by Umbrella Corporation, a pharmaceutical company with secret, sinister plans that involve the creation and sale of BOWs, or Bio-Organic Weapons.

While the others were commanded to engage in a cover-up of the situation, T-00 was given two unique missions - to eliminate any survivors in the Raccoon City Police Station, and track down a sample of the G-virus, a mutagenic pathogen enabling immense growth and power, by any means necessary.

[8] While being temporarily incapacitated by the impact of a moving van and explosives detonated by series antivillain Ada Wong, he later recovers before being seemingly killed by William Birkin, a mutated scientist who formerly worked for Umbrella.

[14] Jordan Boyd of DualShockers hailed the 2019 remake's Mr. X as one of the best developments in the survival horror genre in recent years, citing his unpredictability that forced players to change their playstyle depending on his actions.

[15] Similarly, Alex Donaldson of VG247 dubbed Mr. X a "perfect panic-inducing enemy", also praising its excellent implementation, persistent danger, and ability to turn the game into a horrific experience.

"[18][19] Willow Green of Empire described Mr.X as one of the greatest video game characters, stating that it "relentlessly pursuing our heroes, he was designed by Capcom to offer a different kind of opponent from the usual hordes of shuffling dead-heads.