A large vertical cave has a constant, strong wind blowing out of it from the bowels of the earth. If one was to jump into the currents they would have a controlled ascent on the winds till they reached a height where their weight and the winds force reached equilibrium. Impossible to climb down naturally. What is it? Natural winds from the earth or a complex magical protection for an underground lair?
Mining in a certain area turns all exposed skin (maybe just parts that are actively disturbing the chemicals that cause the reaction) of the those doing the mining to a dark blue color. Will wear off taking as many years/days spent in the mine.
From an episode of Justice League Unlimited:
The God of War creates a giant, unstoppable robot (golem, animated armor, etc.) as a weapon for one side in a civil war; his purpose is to prolong the war and create suffering and war among humanity.
Quote from Ares in that episode, which would go well with this idea: "That's all you mortals are good for! To fight and fight and fight until there is nothing left but charred land and blood and bones, and to end it all and then start again with the next generation!"