Doom

(officially cased DOOM and occasionally DooM by fans, based on the Doom logo)

is the first release of the Doom series, and one of the games that consolidated the first-person shooter genre.

With a science fiction and horror style, it gives the players the role of marines who find themselves in the focal point of an invasion from Hell.

The game introduced deathmatch and cooperative play in the explicit sense, and helped further the practice of allowing and encouraging fan-made modifications of commercial video games.

It was first released on December 10, 1993, when a shareware copy was uploaded to an FTP server at the University of Wisconsin. 

The Ultimate Doom, an updated release of the original game featuring a fourth episode, was released in 1995 and sold at retail.

The Doom Slayer is the protagonist of Doom, Doom II: Hell on Earth, Doom 64, DOOM 2016, and Doom Eternal.

He has also guest starred in the Quake games such as Quake Champions and Quake III Arena.

Source: https://doom.fandom.com/wiki