Significance of Sebau
Sebau are adversaries of Osiris, representing physical forces of evil in external nature. Their defeat symbolizes the triumph of good. They dwell in the Red Sea, conspiring against the elect. The ritual involves battling the sebau, Apap, and Sut, followed by the re-establishment of the earth. The shackling of the Sebau signifies the destruction of Set's fiends when he perpetrates evil again, according to the text.
The below excerpts are indicatory and do represent direct quotations or translations. It is your responsibility to fact check each reference.
Classical concept of 'Sebau'
From: Ancient Egypt the Light of the World
(1) The sebau are described as adversaries of Osiris, whose defeat occurs on the night of the battle, symbolizing the triumph of good over evil.[1] (2) The sebau and the Apap-dragon are whose habitat is in the Red Sea of the mythos, representing the conspirators against the elect, according to the text.[2] (3) In the Ritual the dissolution and re-establishing of the earth by setting up the pillars, immediately follows the battle with the sebau, the Apap, and Sut.[3] (4) They represent the physical forces in external nature that made for evil and were forever opposed to the Good Being and to the peace of the world.[4]
From: The Book of the Dead
(1) The shackling of the Sebau signifieth the destruction of the fiends of Set when he worketh evil a second time.[5]