Hi there,
There is more to your story than I know, but i can tell you ive heard many folk say they see or feel these energy's the night before a close loved one passes, you saw a scull often people see them as men in capes.......the angel of death is a good guess, but i dont think its quiet right ??
Entities cant change the energy they transmit what we think or feel is what we transmit. Loving people transmit love, creepy people transmit creepy.
I have felt that creepy feeling for many years and its mostly associated with dark ets or aliens. Blue orbs can be seen durring the day when they are around. When we board there ship to destroy them they blow up into green dust.
Are you sure it was only 30min of time you lost?? have you ever had an unusual experience that defies logic and is unexplainable?? any bright lights or small lights moving around the room like a torch??