Just so you know.
Demons are not to be taken lightly,
They can perfectly mimic those who are dead,
If you ever see the "spirit" of your dead relative, just completely ignore it, they wan't to manipulate you and cause harm.
On the other hand not all "spirits" are demonic,
They could be a soul in purgatory given permission to show itself to ask for prayers to get to heaven faster.
(I don't know if you would believe half of this but it is what i truly believe)