InstaFiz
Slime Collector
you have to remember the place the old man spawned. When you place platforms on that spot, then the cultists will spawn.Well i never could get the cultists even after rebuilding the temple and defeating the golem so now what i do i wanna start getting better armor
Make sure the platform is leveled with the door.
And as @Eclair The Majin stated, a picture would be helpful.