Published by Softdisk Publishing
Developed by Gamer's Edge
Platform DOS (Shareware)
Catacomb Abyss was the sequel to Catacomb 3D (which was developed by id Software) and it was the first 3D game and the first FPS I ever played.
To be honest, I knew exactly why I was scared, the graphics were a sensation at the time it came out (remember: it was one year before Doom), but when I played it I couldn't believe how much a mere videogame would scare me.