The only Mayhem work he ever does shows up on albums like these, Darius too ~
http://lapfox.bandcamp.com/album/rakugaki It's been a while though so I'm hoping to see some Mayhem soon, and new Negaren comes out every halloween, woot woot.
On youtube, the last mayhem song was posted in July of 2012. He claims to be tired of Mayhem, not the sound just people asking for more of it; he's been looking for new ways to express himself lately so he doesn't get bored, and the new RQ stuff is pretty awesome along with the other shit he's done. All the good Mayhem songs are back in my first post if anyone wants to go find out it sounds like.
And if anyone else is lost, Renard is one guy who has multiple aliases for making different music. All the songs in this thread are by him, despite having different artist names.