The wife of the lead singer of Korn has died Friday ... and it comes on the heels of a request for a domestic violence restraining order and major drug issues ... TMZ has learned.

Deven Davis was the estranged wife of Jonathan Davis. Deven was a former porn star who married Jonathan in 2004. They had 2 kids together.

Jonathan filed for divorce in October 2016, citing irreconcilable differences. Jonathan filed for a domestic violence restraining order today -- August 17, 2018. The judge issued a temporary order blocking any child custody or visitation by Deven. The restraining order also prohibits her from having contact with the family dog, Chaos.

Our sources say Deven was unaware Jonathan filed the restraining order ... she had not even been served.

Jonathan alleged in the docs Deven was deep into drugs -- something she had struggled with for more than 20 years. He alleged her drug use was causing emotional harm to the kids through neglect. He says in his court declaration she has been dependent on both prescription and illegal narcotics. She'd been to rehab 6 times and "is constantly under the influence of the nitrous oxide, cocaine and Norco."

Jonathan claimed she had a drug dealer boyfriend who was recently passed out on her living room couch when he brought the kids to her house. Jonathan says he found a heroin pipe and cocaine floating in the toilet bowl and found Deven passed out on the floor upstairs.

And there's this ... Jonathan claims when she binged on drugs she would "routinely bring home unsavory characters, including strangers. Some of these people are random fans of my music who she allows to come into the house, go into the master bedroom closet and try on my clothes."

According to the docs, Deven had been in a sober home but went AWOL last Friday and hadn't been seen for a week.

At this point we do not know the cause of death.