Forgot Name of Mod - Spawns Enemies

So there’s a mod I used a long time ago and I completely forget what it’s called. It would start waves and play music while the enemies attack you. It could be used on any map and I think the enemies could be either zombies or antlions. Don’t remember if there’s more.

Sounds like a fun addon…
I think i’ve played it, its the one with props with HP, classes and stuff right?

EDIT: Onslaught Evolved?

Nah that’s not it. The music was some heavy metal type music and when activated, the mod would engulf the map in a fog.