Or it represents the title of the album. From wiki:
Later Kabbalistic works, including the Zohar, appear to more strongly affirm dualism, as they ascribe all evil to a supernatural force known as the Sitra Achra[25] ("the other side") that emanates from God. The "left side" of divine emanation is a negative mirror image of the "side of holiness" with which it was locked in combat. [Encyclopaedia Judaica, Volume 6, "Dualism", p. 244]. While this evil aspect exists within the divine structure of the Sefirot, the Zohar indicates that the Sitra Ahra has no power over Ein Sof, and only exists as a necessary aspect of the creation of God to give man free choice, and that evil is the consequence of this choice. It is not a supernatural force opposed to God, but a reflection of the inner moral combat within mankind between the dictates of morality and the surrender to one's basic instincts.