Angels and Demons: Brought Up Evil

Okay, so for my new campaign setting I've included a period of fairly ancient history called the War of Angels and Demons.  During this period of (probably) a couple centuries two groups of powerful beings fought a war over the world.  The Demons sought to destroy life and beauty but also to take control and build war bases.  The Angels came, at first, to thwart the war aims of the Demons but soon took on the task of preserving the life and beauty threatened by the Demons.  In reality both the "Angels" and "Demons" were composed of several allied factions.  After the portals to this world were sealed by the Conclaves of Yin and Yang, the two sides could no longer call for allies and reinforcements.  As the constant warfare wore down their numbers the combatants became more cautious in risking battle.

Today the factions of the Angels and Demons are pantheons of deities reigning over the various areas of the world they controlled when divine warfare ceased.  This means that there are still on-going wars of religion, tensions even between some factions of Angels, and areas ruled by one or more evil "Demon" deities.  For my game I'm going with the concept that deities seek worship by mortals because worship transfers psychic energies to the deities worshipped.  Thus even evil deities seek to amass mortal followers in order to increase their power.  So in the areas held by the Demon deities and pantheons mortals are brought up to worship and sacrifice to their Demon gods and goddesses.  Even in Angel areas individuals and small groups will direct worship to Demon deities in the hopes of being granted powers and given other favors.

So in regions controlled by Demon deities, a capital city might contain an impressive temple looking something like this (thanks to Monsieur Philippe Drouillet):