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.
Basq doesn't exist. He occupies a point in space--a single X,Y,Z point in the Cartesian plane, but he's not made of anything. People looking at him see whatever they want to see. Or what he wants you to see. Usually a mix. Just the same, he cannot be hurt swords or arrows. Only things that deal damage to an area (fireballs, gases) can damage him. Or weapons that can cut through an infinitely small point.