Sefer Tanya by the Alter Rebbe discussions Klippah extensively. Klippah is spiritual shell that conceals G-dliness. There are 3 completely unclean klippos that have absolutely no good at all and must be stayed away from. ie: Non Kosher food. Then there is klippah nogah which has some good in it that needs to be extracted and elevated. ie: kosher food eaten for strength to serve Hashem.
Ch. 1 Introduces Klippah Ch.6 speaks of the levels of impurity Ch. 9 discusses how the Sitrah Achrah and Klippas Nogah comes from the Left side. In ch. 9 the Alter Rebbe introduces the two kings waring to capture the city. Your good inclination vs. your evil inclination trying to conquer the emotions of the heart.
These ideas and more are discussed in early Kabbalah, but the Alter Rebbe revolutionized the understanding of this through Tanya by laying out the concepts of Sitra Achra, Klippos, and a person ability to triumph over evil.
Practical Advice involving Klippos
It says in the back of the Alter Rebbe's Likutei Torah on Parsha Kedoshim Maamar "Hadarta Pnei Zaken" in the name of the Friediker Rebbe that internalizing the first 12 chapters of Tanya will unite your soul levels of Nefesh Ruach and Neshamah. Then with Hashem's help you will triumph over sitra achra and klippa.