Dr. Grant Muller was an antagonist during the events of Tomb Raider: The Angel of Darkness. He was a Botanist and was an expert within his field. He oversaw all activity within The Bio-Research Facility, and created many mutations through his experiments, his most successful being The Pod. His mutations were mostly plants that attacked anything nearby. He was a member of The Cabal and was determined in his wish for immortality.
His only trusted colleague was Kristina Boaz, who was also a scientist (although she worked in a different field). They worked together, creating very many experiements, and were both wary of Pieter Van Eckhardt, the leader of The Cabal. He worked with Boaz in making other mutants around the Facility and The Aquatic Research Area. When Boaz finally managed to create the Proto-Nephilim, Eckhardt ordered for it to be destroyed, as it was a disaster, but Boaz didn't, and Muller condemned this action, claiming she was stupid to do it.
After, Lara managed to infiltrate the Bio-Research Facility. She turned off all power within the Facility, which caused the Proto-Nephilim to escape. Lara encountered Muller in the entrance of The Dome. He claimed that she would be killed, and explained to her that The Cabal would soon rule the Earth, and he and other members of The Cabal would be immortal. He escaped when he used his fertiliser spray to paralyse her. Later, when Muller was trying to turn the power back on, Eckhardt and Marten Gunderson were questioning him on how this could have happened, until Boaz ran in and explained that she hadn't killed the Proto-Nephilim and that it had escaped. Eckhardt was outraged - he ordered Muller to release The Pod, which Muller did, and then Eckhardt threw Boaz into The Pod, which absorbed her whole. Eckhardt started threatening Muller that anymore mistakes would be his last and that he would suffer a similar fate as Boaz. Muller assumed to be let off the hook, but this was untrue.
Later, when the Proto-Nephilim had been killed, Lara and Kurtis Trent were trapped in a large room, where Eckhardt, Gunderson and Muller were standing on a raised platform. After Eckhardt had threatened them, he released Boaz, who was now a mutation after she was consumed by The Pod. Muller wanted to make a quick exit, because he didn't want to see his mutated colleague, but Eckhardt stopped him and said, "Not you Muller, you useless piece of dross! You failed me too!". Then, Gunderson towered over Muller and pushed him off the ledge. As he landed on the ground, he looked at Lara who was pointing her gun at him. He decided to run away from Lara, towards Boaz to try and run past her, but Boaz picked him up and chewed his head.
- He never takes his glasses off during the game.
- It is unknown how he became to join the Cabal or be in terms with Eckhardt.
- He actually has a weapon and uses it to escape from Lara. It seems to be a fertilizer spray that stuns opponents, although its main purpose is probably to nurture his plants.
- He is the fourth last Cabal member to be killed as Eckhardt, Joachim Karel and Gunderson outlived him.
- "No, the power's down everywhere."
- "Yes, Master Eckhardt."
- "Intruders don't last long in The Strahov."
- "We are the beginning of a new order of life on Earth."
- "Ignorant mortal!"