I think one aspect we missed addressing, probably because it is obvious to many folks, is that the work "holiday" has it's roots in "Holy Day". Sure, most holidays in fantasy games are going to be rooted in religion, but many times the trappings will obscure the true meaning of the holiday.
I'd like to see a holiday in game where it's evil roots are hidden by the celebrations, festivities and general excitement of the holiday. The town no longer remembers the roots of the holiday, which were to celebrate the power of Iuz (or some other evil god or power.) This year, the party stumbles into the festivities when the celebrations start having supernatural effects - blood dripping trees, fruit that has miniature fetuses inside the skin and other signs. The town folks think they are doing something wrong - little do they know they are doing everything perfectly right ;)
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