Once you access the Molten front you can glitch your way into the molten Flow. If you follow the path to the furnace (you can avoid the fire by staying to the side of the path)
1.) die near the big rock with cracks in the center of "the furnace"
2.) run back as a ghost
3.) ghost falls threw giant rock with cracks
4.) accept resurrection after falling threw rock
5.) cast something that will prevent fall damage (slow fall, bubble, heroic leap) or die and run and fall back threw
you can use this area to:
talk to Thisalee Crow for "Fireside Chat"
get the achievement "Master of the Molten Flow"
you can use the thermal vents to jump on top of rocks (I did find 1 chest on top of some rocks) (thermal vents are the wind like things that flow up and allow you to jump really high)
to leave this area just go back to where you fell in and jump there is a thermal vent that will take you back to the top.