I host an event at my school once a week, in this event (which is 90 minutes long), we play a multiplayer PC game at my high school (we have permission since it's during advisory). The first time we played Civilization II: Test of Time, then the next two times we did Total Annihilation (with both expansion packs; The Core Contingency and Battle Tactics), and this week we are doing Half-Life (non-Steam) with Team Fortress Classic and Deathmatch Classic.

I would like to bring in a few other mods for Half-Life (non-Steam) too, does anyone know a really scary mod for Half-Life (compatible with the non-Steam version of Half-Life)? And by scary, I mean really scary (and multiplayer of course, like co-op or something), where it will be like dark most of the time (or with blinking lights), and monsters that jump out at you and just scare the begeezes out of you. The version of Half-Life (non-Steam) we are playing is 1.1.0.8.

Please recommend the scariest mod you know (that is compatible with Half-Life 1 version 1.1.0.8, and non-Steam, of course). Also, please link to where we can get it and the official website if possible. Also, it has to be multiplayer (or atleast have LAN multiplayer support, and it has to be cooperative). Thank you so much for your help.