天下英雄 關聖帝君 依幕處 近廳天地 八位諸將
천하영웅 관성제군 의막처 근청 천지팔위제장
Eui-mak-cheo Geun-cheong Cheon-ji-pal-wi-je-jang
六丁六甲 六丙六乙 所率諸將 一別屛營邪鬼
육정육갑 육병육을 소솔제장 일별병영사귀
Yuk-jeong Yuk-gap Yuk-byeong Yuk-eul
Gang Jeung-san's successor Go Su-bu said about the Gwanseongju Mantra:
"It helps you to get rid of evil energy, to release the devils, to make your mind unwavering, and to remove obstacles/disturbing."
[Source: 'Seonjeongweongyeong', written by Go Min-hwan, a follower of Go Su-bu]
Getting rid of evil energy means, all the spirits which have negative qi will be cleared away from you. However, you shouldn't consider devil spirits ("ma") to be the same as the spirits which have evil qi. Devil spirits exist in order to help you becoming aware of mistakes you made, so they give you suffering for a reason. By chanting the Gwanseongju mantra you receive justice/righteous qi, which helps you to see what is wrong in your mind and needs to be fixed. After doing so, the devil is leaving by itself. You can only truly understand this when you know about the spirit world through enlightenment.
You shouldn't think that all the spirits are of the same kind. Devil spirits also need to be distinguished from vengeful spirits, which only focus on revenge because of their hateful relationship with you. Vengeful spirits are not evil spirits either. They simply became vengeful spirits because they got hurt by you in a previous life.
The Gwanseongju Mantra helps you to fix your mind, because you can see what you did wrong by receiving access to justice/righteous qi. Therefore, you shouldn't chant this mantra with a selfish mind by simply thinking that the mantra will kick out all the spirits which disturb you. If you chant this mantra with the wrong mind you will bring bad luck upon yourself.
Source: Gang Jeung-san Sangjenim
Correction & Transcription: Jinju2Saram