|Function(s) / Belongings|
|Rank / Occupation||
Level 5 Scientist
|Chronological and political information|
Keller is a wheelchair-bound scientist working at the Anomalous Materials Laboratory. He monitors the experiment from a control room below the test chamber. Despite Dr. Rosenberg's warning, he allows the science team to run the Anti-Mass Spectrometer at a great intensity than it is designed for, although he mentions that it is the Administrator who ordered this.
After the Resonance Cascade, he assists the players by communicating with them through the audio systems of their suits to help them orchestra a resonance reversal to seal the dimensional rift between the worlds and stop the alien invasion.
 Personality and skills
Keller is portrayed as being a temperamental and somewhat contemptuous person in the game. At the start of the game, Keller has a quite harsh temperament. He tends to mock or blame people with ironic remarks. Before the Resonance Cascade, he gives his views about Gordon Freeman's frequent late arrivals, then questions his skills, stating he does not understand what Isaac Kleiner sees "in that boy". It is also hinted that he carries a grudge against his colleague Rosenberg; he mocks him and his "little labs by the trainyard" when the latter expresses his concerns about running the Anti-Mass Spectrometer at too high of an intensity, and answers him harshly most of the time. After the Resonance Cascade and for the remainder of the game, his attitude is softer somehow, although he is still very tough if the players fail a mission. At the end of the chapter Resonance, he shows himself to be suspicious about what or who is behind the events, saying "[the] aliens may not all be here by accident".
On Keller's wheelchair is a remote that is possibly connected to the Black Mesa network, as he is seen to open doors with it, among others.
 Behind the scenes
- Keller was originally slated to be Dr. Kleiner, the professor and mentor of Gordon Freeman. The textures for his character model even still bear the prefix "Kleiner". In a similar manner to how they utilized Gina, Gearbox wanted to try and leverage Kleiner, who until that point had only been mentioned in the original instruction manual. Valve was always supportive of the company using their characters, but this concept had to be scrapped early on as Valve had other plans for Kleiner for their own in-development Half-Life 2.
- David Mertz suggested Keller to place him a wheelchair to give him a bit of a character. This suggestion also included the idea that Keller would get up out of his wheelchair and walk at the end, revealing that he was not what he appeared, a manipulator, a bad guy. This walking animation can be found in the files of the final game.
- There is an unused audio clip for Keller only present in the international releases of the game. In this line of dialogue, Keller wishes the players good luck and leaves them in the last mission. According to Matthew Armstrong, this line is from when Keller was still Kleiner in the storyline, but his actions no longer made sense when they changed him into a new character, leaving this part to be cut.
- It is implied that Kleiner incarnation of Keller may have had a hand in the onset of the Black Mesa incident. It should be noted that Kleiner was the one who recommended Gordon and got him hired at Black Mesa. Gordon may have been purposely hired to act as a scapegoat in the wake of the experiment's failure.
- Richard Keller is the first and only disabled person to be seen in the series (disregarding Eli Vance's missing leg in Half-Life 2, not really disabling him), along with the first female employees, Gina Cross and Colette Green. In the three games preceding Half-Life: Decay, the only hint of disabled persons working at or visiting Black Mesa was a wheelchair emplacement in the Black Mesa Transit System monorail, a Black Mesa Announcement System note about disabled personnel during the Half-Life and Blue Shift tram rides along the Transit System, and parking spaces for disabled persons in the underground parking lots in Opposing Force. In Decay, this emplacement is used by Keller. Other examples include two wheelchair ramps in the North Wing of the Level 3 Dormitories, and a wheelchair elevator in the Gamma Labs. The brand of Keller's motorized wheelchair is Invacare, an actual manufacturer and distributor of non-acute medical equipments, including wheelchairs.
- Except for the tie and the badge, Keller is the only Black Mesa scientist to be seen not wearing standard scientist outfit (thus a lab coat or a HEV Suit).
- As seen in the Hazard Course Training schedule from the Half-Life PlayStation 2 instruction manual, Gina Cross tests a Mark V HEV Suit prototype under Keller's supervision on May 15, 200- at 20:00.
Rosenberg and Keller in an argument.