How about showing the things that this monster has destroyed? Other humans, who, the player's character knew before, just massacred, torn apart, and scattered around, might help the horrifying setting, especially if the dead ones were stronger than the player.
but given that what techniques are available to show that it's getting close and keep the player on their toes?
Things such as only showing only limited view of the monster might help. You see a massive claw reaching out from the corner of the room for you but you can't see the whole monster? That would be scary if done right. You hear the monster walking around, stops, starts sniffing the air, and then you hear the monster suddenly start running towards you. You're at a dead end and you hear someone or something cry right next door and you have nowhere to run except towards the screaming.
That's all I can think of for now.