I get my black wax and silken codex from the last hallway in The Wakening on heroic. Right before you get to the Ogre and thrall there are 4 yellow acolytes, a yellow knight, and red knight. Kill the yell knight with 2 ice breaker head shots and the rest with the fang and field scout. If you get really good it takes under 30 seconds. Kill yourself with a grenade and the vestige on the left and you'll respawn right at the same place. Rinse and repeat. This is also the best and simplest place to farm glimmer. Most just don't know about it.