about seeing demons while in 'dark' places; it's certainly possible.
the enemy loves to scare us, but we don't need to be afraid.
james 4:7 'submit to God, resist the devil, and he will flee from you'.
about 'ghosts'; these are usually also demons (read below for the info about yr deceased relative, this is not in this category). the demons love people to think that a dead person can come back and 'haunt' them, and they love to terrify people with things that go 'bump' in the night. (remember most things that go 'bump' are simply expanding floorboards in the heat, plumbing, mice under the floorboards etc and are totally natural).
demons can cause all sorts of manifestations, and they want people to think they are dead people as this causes more confusion, and it causes people to try to contact the dead, which God has forbidden.
God has not given us the power to initiate contact with the dead, only God initiates this.
when we initiate it (seance, tarot etc), we exhibit pride and rebellion, and the enemy takes the opportunity to push us further from God by making these things 'interesting' with supernatural experiences that have nothing to do with the dead person.
we Christians do not believe that a 'ghost' is the spirit of someone who has had an unpleasant death and so is not at 'rest' in the spirit world. this is a pagan belief. a 'ghost' is often a trick (fake) by a magician or it could a demon wanting to confuse our minds and open us up to the world of 'spirits' (demons) who love to mess with our brains.
we should avoid this at all costs.
however, if someone has a spontaneous experience (not trying to contact the dead) of a feeling of a deceased person together with positive emotions such as peace and love, it MIGHT be an experience God allows us to have to remind us that His is in control of the living and the dead. if we get this experience, we should make the sign of the cross (as the saints always did) and focus our thoughts on Jesus, being willing for the experience to cease if it is not from God.
we should not become proud and think that all our experiences must be genuine; rather we should recognise our weakness and be careful unless the enemy deceives us and makes us proud.
this is why saint antony the great used to assume 'the devil told me', when he had some supernatural knowledge, so that he did not become proud.
this link above also has lots of good advice for avoiding pride in your spiritual life.
i have had a few strange experiences myself, but i will follow the advice above and not post them here.
may God bless u all and guide u, and please pray for egypt and for Christians around the world who suffer for their faith.