Invoke Set (Seth) if you want protection or to get rid of negatives or unwanted spirits or to ward of those that fear him or want to see that harm comes to you. As he is the God of trickery, be very clear why you are invoking him - and be prepared for the resulting chaos. Seeing Set in a dream means there may be negative spirits or that protection is needed.
Who hast no nature and no name,
Who art, when all but thou are gone,
Thou, centre and secret of the Sun!
Thou the child of Geb Thy Father and Nut thy Mother.
O thou whose skin is white,
Thou who defends the boat of Ra,
O thou whose hair is as the red as the earth of the unconquered desert.
O thou that didst join us in war with the gods,
O thou who bearest the Was Sceptre!
O thou, Great of Strength,
O thou black boar,
O thou Lord of the Oasis,