The level 3 armor chest is at the top of the hanging bridges in the Midnight helix chamber.
It spawns rift crystals and level 3 armor only it seems. The drop rate for the armor is pretty good though I've never had to Godsbane more than half a dozen times to get the armor, nowhere near as bad as the Everfall.
The chamber seems to have two different enemy types a GoreCyclopse which is easy, and a Dragon of some type with the red flying gargoyles - I avoid that one. It seems if there are Goblins in the first hall of Bitterblack than the cyclops is there, but if it's Saurians than you'll get the dragon.
I'm avoiding farming the final boss because I don't want to burn out on the final levels of this game getting weapons.
The level 3 gear and novelty chests are side by side just after that courtyard where the two cyclops are chained up and those sorcerers are casting maelstrom (I can't remember the name at the moment). As you are in the hallway leaving to go down there is a passage on your right where you have to climb up through a hole in the floor. There are money bags and two chests.
No one has a weapon chest location? I'm thinking there has to be at least one somewhere.
Another lvl 3 armor chest is right b4 you go to fight the final boss. B4 u go up the narrow path where 3 enemies block the path, look for the hay stack and climb over the wall closet to the edge and the chest gives either a perfect rift crystal or lvl 3 armor.
When you are a child, anything is possible. When you're 30 you've made your bed. Life doesn't have a reset button.