To achieve the achievement Nosalises hunter, firstly load up the level dark star
once you have loaded this level up and you have experienced the vision grab the flamethrower from the crate on the left side (it will be behind you)
once you have picked the flamethrower up, wait a short while and the lights will turn on. a horde of Nosalises will appear and continuously charge your rail car.
Light them all up with the flamethrower until one of the npc's exclaimes "Last Switch!"
Once they have shouted this out reload the checkpoint and rinse and repeat until the achievement pops
Hope this helps.