Prime universe
(Capcom's primary storyline)

"Too much growth weakens an organization, what should be important becomes overshadowed by greed! Mass production?!? Ridiculous!!!""
— Greg realizes Umbrella intends to mass produce Thanatos.

Dr. Greg Mueller was an Umbrella virologist who rebelled against the company, albeit to serve his own ends.


Greg was assigned to the Umbrella R&D Center in Raccoon City.[1] After William Birkin assigned his t-Virus project to Greg, during his time there, he was involved in the events surrounding the Arklay hospital and the illegal human drugs trials being conducted on the outskirts of Raccoon City.[2]

Some time in 1996, one of his students, Yoko Suzuki, was involved in the t-Virus project by donating her cells. Greg operated on her to alter her memory, removing any recollection of her involvement in the experiment.

At one point, he began researching into the experimental "Tyrant"-class B.O.W., which he attempted to develop single-handedly. The fruit of his work was "Thanatos", a seven-foot-tall killing machine. Unlike other B.O.W.'s created that year, Thanatos far surpassed them all in intelligence, strength, and agility.

However, when Umbrella began plans to mass-produce the Tyrant, Greg became furious, believing that this would take away from the individuality and uniqueness of his subject. Like many Umbrella researchers, Greg viewed his creations as pure works of art, not mass-production weapons as Umbrella intended, and refused to assist them any longer.

To further spite Umbrella, Greg provided aid to Dr. Peter Jenkins, a Raccoon University professor, in creating a cure for the t-Virus; Umbrella's most prized viral weapon, intending to remove Jenkins after the completion of the "Daylight" serum. However, as Peter's suspicions regarding Greg's past started to become apparent, he was forced to execute him before the process could be completed, leaving Greg without the final necessary information required to complete the Daylight formula.

Due to his rebellion, Greg was marked for assassination by Umbrella, who sent a U.B.C.S. team to assassinate him and retrieve a blood sample from Thanatos in the early hours of October 1, 1998. Anticipating this, Greg intended to have Thanatos eliminate his would-be assassins, and Thanatos largely achieved this, quickly killing off the U.B.C.S. task force sent to carry out the mission. However, a U.B.C.S. observer, Nikolai Zinoviev, ultimately succeeded in executing Greg via shot to head from above the ceiling in the Second Hall of Raccoon University, of which Greg never even saw coming.


"Too much growth weakens an organization, What should be important becomes overshadowed by greed. Mass production?! Ridiculous! [...] One masterpiece is enough!"
— Greg in the opening cutscene of Decisions, Decisions.

"My apologies for this place being so... hectic. I have been monitoring your progress from here. I am grateful for your assistance. Daylight is it. The only resource against the T-virus. I cannot give it over to Umbrella. They're the ones responsible for the catastrophe which has befallen the city. In retrospect, the entire "t" project was a total disaster. Brute force should not be the only criteria for a weapon. It must also be beautiful, unique, and God-like. You will also assist me. You're going to play with my ultimate creation."
— Greg talking to the survivors in the Second Hall.

"Yoko, it's been two years... oh, but you might not know that. After all, what happened was so terrible... I think you'd want to erase it from your memory."
— Greg talking to Yoko in the Second Hall.


Greg is unlocked after completing the scenario Decisions, Decisions on VERY HARD difficulty. His set costs 10.000 points. Alternatively, he is already unlocked in File #2 and can be purchased for a much cheaper price (1.000), and can be transferred to Outbreak via the Data Convert.

The following is a translated adaptation of information found in the BIOHAZARD OUTBREAK FILE 2 GRAND BIBLE.

Infection rate
1.21% per minute
Movement speed
Attack modifier
Starting condition
Starting items
Anti-Virus (L) (Outbreak)

Anti-virus X3 (File #2)

The following is a transcription of information found in the BIOHAZARD OUTBREAK FILE 2 GRAND BIBLE.

1.21% per minute
Anti-Virus (L) (Outbreak)

Anti-virus X3 (File #2)


  1. Resident Evil Outbreak File #2, special item: "Gold Glasses".
  2. Resident Evil Outbreak File #2, file: "Sealed Letter".