One of the Apparitions should be a woman's ghost that comes stabbing overhead at the screen slowly advancing with a knife pointed downward until the alarm sound , at which her head looks up at you and she raises the knife and it begins phasing in and out left and right of the center of your screen advancing with a creepypasta grin , have the proper escape route to be to run straight backwards and veer left or right while shooting and her and trying to not get poked! In imagining this Foe ,I'm thinking of House of the Dead 2 1st level Boss stuff specifically, oh and lemme know if you know the guy i mean he is a boss at the end and it is like he is locked to the screen, so when he touches a wall he can become phased out for a random number of steps and then he re-appears somewhere onscreen and also once taking certain number of damages he will changed sides... I haven't played that game in a long time but I believe this is the perfect example of that mechanic in action for your end of that if you so decide to try doing this one.
A Chick running with a knife overhead is just plain scary to me pal ! lol