: also was is the significance of the eruption of Tharsis
: does that really have anything to do with The Leveller or
: is it just some GURPS BS?
Tharsis erupted in Myth 1 "for the first time in a thousand years". Seems like a Leveller thing to me. My guess is that the world in general is in upheaval around then, so it's no wonder that this big hole in the middle starts spewing fire. Or, or you wanna get technical, maybe some gravitic properties of the comet causes certain tidal effects in the Mythworld's crust, causing an eruption from the only volcano in the world.
