The following is reconstructed from forum posts, secondhand accounts, and the documentation that accompanied the only known surviving copy of Killswitch, sold on eBay in 2005 for $733,000 to a buyer who has never been publicly identified.
Background
Killswitch was released in 1989 by a Czechoslovakian developer calling itself the Karvina Corporation. It was distributed in extremely limited quantities — estimates range from fifty to several hundred copies — through mail order only, with no retail presence. No advertisements for the game have ever been found in contemporary gaming magazines or catalogs. The mechanism by which early players obtained it is not known.
The game was a survival-horror adventure with primitive but allegedly effective graphics. Players navigated a coal mine following a gas explosion, searching for an exit while managing oxygen, injury, and visibility in the dark.
The Two Characters
Killswitch offered a character selection screen at startup: a man named Porto, and an entity described only as Ghast — invisible, unrenderable, a character experienced entirely through the sounds around it and the reactions of environmental objects. Porto played as a conventional survival game. Ghast played as something else entirely, a game of pure inference where the player could only determine their location and the state of the world through audio cues and the movement of objects they could not see themselves move.
Completing the game as Porto triggered the ending cutscene and returned the player to the title screen.
Completing the game as Ghast triggered the ending cutscene — longer, by all accounts, and deeply disturbing in ways that survivors struggled to articulate — and then permanently erased the game from the hard drive. Not just the save files. The executable, the data files, every component of the installation. It overwrote the sectors on the disk. Players who attempted to recover the data with contemporary tools found the sectors filled with a repeating string of characters that transliterated, roughly, from the Czech, to: "I'm sorry. I'm sorry. I'm sorry."
The Surviving Copy
The eBay auction in 2005 attracted significant attention from gaming historians and collectors. The seller, who gave only initials, claimed the copy had never been run. The documentation included a handwritten note in the original packaging, in what appeared to be Czech, that translated approximately as: "For the one who waits. She will be patient. She will understand why she cannot be seen."
The winning bidder paid $733,000. They took possession of the package. They have never publicly stated whether they ran the game, which character they chose, or what they found.
Addendum
A researcher who spent several years attempting to locate additional copies of Killswitch eventually found what appeared to be a partial listing in a 1989 Eastern European mail-order catalog. The game's listed description, machine-translated, read: "A game about loss. One path survives. One path ensures no path remains. The player chooses. Karvina Corporation is not responsible for what the player chooses."
The Karvina Corporation has no verifiable corporate history. No employees, no address, no tax records from any jurisdiction.
The game exists in one copy in an unknown location.
Porto waits at the mine entrance. Ghast waits in the dark beside him.
One of them will erase everything when you reach the end.
You won't know which one until you've already finished.