Also worth mentioning is that dying is not scary, but being afraid of dying is. Always try to keep the player on his toes but make sure there are no places where he has to actually repeatedly die to learn something. Dying takes away the fear of dying and also the mystery about the monster. Also, leads to repetition which is boring.

You'll probably need a certain rule set for the game that you convey the player. "It can't come here because it's well-lit area". "It can't jump so you're safe up here". Then, later in the game, take away that "safe spot" mechanic. "It ran into the fuse box outside the door and the lights went out". "It climbed on the boxes and broke the railing". "It shook the columns and the catwalk broke." "It went through the ventilation duct and now lunges at you from ceiling". Tell the player "that might have worked before but it doesn't mean it's going to work every time" but be rational about it of course. Make the player to be in lookout for places where it might ambush them.