Indeed, they can and do deceive humans, even Christians, with their apparitions.
2 Cor 11:14 -
“And no marvel; for Satan himself is transformed into an angel of light.”
Matt 24:24 -
“For there shall arise false Christs, and false prophets, and shall shew great signs and wonders; insomuch that, if it were possible, they shall deceive the very elect.”
I have 2 souls that have never left me,my Mom and Father J.Their presence is with me and they guide me along with St Joseph and Our Lady.