The Lord is real, just as evil powers are real. He gives to you, if you would trust in the Lord Jesus Christ for your welfare. Not as the peace the world gives, but His peace that passes all understandings. He loves and care about you. Nightmares are not just empty dreams.
Spirits can get into dreams to teach, to deceive, to scare, to tempt people.
Be on guard and be in Christ that you may be ready to resist all evil, and to discern vision.