Tis the season for mistletoe, so this should be relatively easy to obtain. It is a most magical herb that, when hung on the headboard of a bed, has the ability to protect the sleeper not only from danger but from nightmares as well.
To empower the mistletoe with your intention, hold it in both hands and envision it surrounded by pure white light. When you feel the power is at its strongest, say:
Golden bough of magic might,
Hang the mistletoe on the headboard (behind it is fine) of the bed. One of these charms can be made for each bed in your home.