Entities spawning on map load?

I’ve been looking for a script or addon that allows entites to be spawned on map load. (Specified in a file, or perhaps a ‘save and load’ system…)

I know I’ve seen an addon like this somewhere, but I forgot the name, as I didn’t need it before.

Any links, or perhaps even a rough script would be eternally useful.

I’m not entirely sure if this can save entities but you can give it a shot.