Medallions
1: In the bathroom in apartment 5
2: In the back room of apartment 2
3: In the back room behind the counter, in the pub
4: In the room with the dead cows after the Devil's Flower, remember to check the brown doors
5: On a table in apartment 11

Skulls
1: On a shelf in apartment 4
2: Freezer room, storage room of the dining room
3: In a corner in apartment 8
4: In the room left of the doors to the pub
5: Behind one of the white metal doors in the hallway leading to the door that requires the five medallions

Codes
Devil's Flower: south, west, north, south-east.
Spider chase: 1794