I just had a moment of sudden clarity. Having been such a big fan of Warhammer Chaos for so many years I have no idea how I never realized this before. Perhaps everyone else allready realized this and I was just being slow:
Look at the symbol of Tzeentch:
In a lot of versions of that symbol, it looks like a disc with a waning moon behind it. The waning moon being more or less twisted.
This is actually the two moons of the Warhammer world. The disc is a full Morrslieb with a waning Mannslieb behind it. The twisting powers of the full chaos moon distorting Mannslieb on Geheimnisnacht (the one night of the year when Morrslieb is full and closest to the world and the night where sorcerors of Tzeentch are at their most powerfull).
I'm sorry, this might not be interesting to many others but I just love suddenly discovering new tidbits of the setting that I have missed until now. Warhammer is a setting that just keeps on giving
Edited by Ralzar, 14 October 2013 - 03:29 AM.