| "I once thought I could save the world... now look at it"
— Spoilers for Deus Ex: Mankind Divided follow!
Václav Koller (pronounced [ˈvaːtslaf]) is an underground augmentation specialist based in Prague, Czech Republic. He owns a book shop named The Time Machine in Prague, and his clinic is in an underground area below the shop, accessed through a secret bookshelf door.
Koller acts as Adam Jensen's personal neuroplastic surgeon during his stay in Prague.
Koller is an eccentric engineer who has used his skills to augment himself extensively  and deals with both standard and controversial augmentations.
He has associations with many of the factions in Prague, including organized crime. In particular, he is under the protection of the Dvali crime family. It is revealed that their leader, Radich Nikoladze, has a secret leg augment, so Koller maintains it and is given protection in return. However, Otar Botkoveli is unaware of the reason behind this protection, so he tries to get to Koller as a way to get to Nikoladze.
Koller also reveals he does not agree with Talos Rucker's philosophy that they should take a peaceful approach to making things better, as Rucker was "making us [Augs] look like wimps" and is happy that he is now dead. When pressed about it, he will simply say that he felt Rucker was not the solution and they need a leader who will actually fight the discriminatory laws, like the Human Restoration Act.
- As a child, Koller was already augmented. At the age of 8, he was caught by his mother during the act of soldering the circuits from a toy gun to his mechanical arm.
- After Jensen returns from G.A.R.M., Koller may be found dead on the chair is his clinic with a monitor that says "He had a deal" on his lap.
- This happens if Jensen had entered into an agreement with Otar Botkoveli, but failed or neglected to complete the two favors for him, prompting Otar to murder Koller as retaliation. Jensen will receive a call from Otar shortly before killing him, with a tortured and barely alive Koller calling for him in the background.
- Alternatively, if Jensen does complete the two favors and does not kill Gallois, then it is Nikoladze himself who will order the hit on Koller since as Gallois was Radich's Neuropozyne courier, removing him from the picture means that the deal is broken.
- This seems to have been fixed in a patch (version 1.05), as Koller will still be alive if Jensen took the non-lethal approach with Gallois. However, Nikoladze still appears to be in power even after doing Otar's favors. This is possibly another unaddressed bug.
- One way to save Koller properly is to either kill both Otar and his henchman Vano, therefore forfeiting several side quests and achievements (one of them being Pacifist), or complete both favors for Otar then murder Gallois when given the opportunity. Once Otar has usurped Nikoladze, he will have the latter killed but spares Koller in return for the favors he now owes Jensen.
- For an Otar-alliance Pacifist run, Gallois can be provoked into attacking the player via dialogue and the local police will promptly have him gunned down without any interaction from the player.
- Jensen pronounces Koller's first name with a soft "c" instead of the proper "ts". Even Koller himself pronounces it this way about half way into the story, when he hails Jensen over to fully calibrate his system to be compatible with his experimental augmentations.
- ↑ 1.0 1.1 Character information on the official Deus Ex website
- ↑ Character info, in-game loading screen