3D Monster Maze is regarded as the earliest horror game created for computers. The game was first played on the Sinclair ZX81 in 1981. The player is put in a maze with only one exit and a hostile T-Rex dinosaur. You, as the player, through a first-person perspective, must escape without being eaten. Happy Halloween!
3D Monster Chase for the Amstrad PC released in 1983 can be played online via archive.org Mame emulator (thanks to Romik Software).
Game Description: “3-D Monster Chase is 1st person perspective maze game where the aim is to collect seven keys as well as defuse bombs while avoiding monsters. The maze is made up of three floors which can be moved between by lifts, and each key must be found in order. Once you find the key, you would return to your starting position and place the bomb in the maze. The bomb needs to be defused in a period of time before it explodes, or you lose one of three lives. Once the bomb has been defused, then you must find key one again before you can find key two, and this is the sequence the keys must be collected for all seven keys. As you search the maze, monsters start to appear, and a monster keeps appearing after a period of time. If you are caught by a monster, then a life is lost, but you are armed with a limited amount of grenades to throw. There are five skill levels (1-5), with one being the easiest.” mobygames.com