Wow, you really look into every corner of the map.
I would not set my expectations too high as it could just be an easter egg, a small nod to Episode V, and not actually contain something in the way of a reward.
However, I did notice that there is a burning oil pool near the beginning of the operation, before the first boss in the outdoor area with the larvae.
I managed to stay in the flames with the debuff stacking up to x10 with a moderate amount of healing, but nothing happened. In hard mode, maybe you will get a debuff there when you stay in the flames for some time.
Anyway, it's great to see players trying to figure out the riddle, and I am looking forward to when the solution is found!