DN1: Mary

Information and Basic Mechanics shared between versions
This is the main enemy in Dungeon Nightmares and probably the most iconic enemy in the entire series. She looks like a mummy in the first game, but in the remastered version and in the second game it gets pretty clear that she is actually not a mummy, but a burnt woman still covered in blood. She wanders, looking for the player, or “she waits around every corner”. Once she finds the player, she will throw a sudden and loud scream and then she will start chasing the player, until she kills them, or loses them in the distance. While in a chase, a scary repetitive metallic sound is playing in the background and her screams can be heard when not far away from her. Once these sounds die down, it means she lost the player. While chasing the player, she is walking at about the same speed as when the player walks, so, it’s quite easy to lose her, especially when running. However, this can change under certain circumstances.

She can be found either wandering in the hallways, or just standing still inside a chamber, waiting for the player to bump into her. She cannot see the player from afar and neither can she be seen from a very long distance. However, when she is facing the player, she can spot them from a longer distance than the player can, especially if the player has a candle lit. While in a chase, the player can delay her movement by closing doors behind them. She will need some time to open the door, meaning that this way the player can buy lots of time to lose her ("Close doors to slow them down"). When the scary chase sound effects stop playing, she will still move towards the player, until she loses interest, she may even reach the door of the chamber the player is hiding into.

The game initially makes players believe that Mary is always somewhere in the map, wandering, seeking the player, but this is in fact not the case. Some tips in the loading screen, or notes found give the player hints about the true mechanics of Mary. Examples:

"Day 6: Something saw me and chased me into this room... It went away after I closed the door"

"Day 14: I found Mary in a room today... She wasn't there earlier"

As these hints imply, Mary actually spawns, disappears and respawns at different specific points, more specifically, chambers. Just after the game starts, Mary is nowhere in the map. The time it takes from the beginning of gameplay until Mary spawns somewhere depends on the night. The more advenced the night, the sooner she will spawn. She usually spawns in chambers close to the player's location and waits there, or opens the door and starts wandering in the hallways, opening doors while doing so. When she spawns and is really close, she will sometimes come towards the player's location (“Keep running, they know where you are”). When Mary is nearby, BGM stops and only the heartbeat can be heard. When close to a corpse, a fly can also be heard, sometimes covering the absense of BGM. If she never finds the player, after some time, she will disappear and BGM will start playing again. If you encounter an open door, but BGM is still playing, this means that at some point, Mary spawned there and she opened that door, but she never found you. Progressing to the next nights, the frequency at which she spawns increases. She also tends to spawn even closer to the player's location. In Night 7, it is possible to run into her in under 30 seconds after starting the game. It is also possible to run into her without BGM dying down, because the BGM doesn’t stop immediately and it needs some seconds until it stops completely.

ORIGINAL: Specific mechanics
While in a chase, if the player fails to escape Mary for too long, the next time she gets close to them, she will throw a low frequency roar (almost like a man, or monster screaming) and start running non-stop. If this happens, it is very difficult to escape her, as she moves fast enough to pass through a closing door before it closes completely. This will almost always result in defeat, especially in the last 3 nights, where she cannot be stunned by taking advantage of the first hit to the player (read below).

In Nights 1, 2, 3 and 4, she has to harm the player twice for the game to be lost. In Nights 5, 6 or 7, she can kill the player with one hit. This means that in the first 4 Nights, there is hope for the player to escape her even if she is already running. Once she harms the player she gets stunned for a little while, enough to close a door nearby and successfully block her route. But it is impossible in the last 3 nights.

REMASTERED: Specific mechanics
Some of Mary's mechanics differ from the original game. She seems to follow a different algorithm to follow the player. In the original game, Mary always follows the path the player makes on the map, whereas in this version, she is aware of the player's exact location on the map. She frequently uses shortcuts to catch up to the player and she even gets stuck in a corner, trying to get to the player via a straight line, when that is not possible by a little. This sometimes leads to surprise attacks, because there might be a shortcut not yet discovered by the player. She also doen't seem to be able to run. However, she can freely clip through objects like tables and barrels and even the Exit.