I want this to be the focus of a save-the-town quest. Everyone is starving, quickly! Find and lug the heavy stone object through the dungeon, across the rickety canyon bridge (WHUMP!), over the lake in the leaky boat (*gurgle*), up the hill, up the hill again, (Damn you Sisyphus!) et cetera. It makes me snigger with evil DM delight.
I quite like this idea because it is highly adaptable. If your game does not focus on Ether a similar setup could be made for any 'aura' of your choosing. What a perfect way to harken the arrival of the BBEG, chimes ringing furiously in a place absent of wind but with a darkening sky. They could also function like Tribbles + Kingons, which is to say if some ethereal/evil has posessed a human or is disguised they still react. They're just a really nice touch that can be added anywhere.
I am not going to vote yet, because this is so close to being a five but is missing one crucial thing to me. Motivation. What is the mission of the circus? Why does this god value laughter? Why does he have a group of laughing assassins? I feel like all of this could be explained if I just knew what the motivation of the cult or their god was.