Starting with a clean slate of comments, huh? xD

Silent Hill Week - For three, four, or five days Asgard; Niflheim; Emptiness; and the surrounding areas are 'invaded by the otherworld'. A thick mist hangs in the air, the buildings (except for maybe the Asgard, and Niflheim mansions) are run down, walls are covered in rust stains.

And that's just the misty version. At unpredictable intervals a siren, or the sound of an electro shock will be heard just before the place is twisted into a nightmare. And not just any nightmare either. The place would twist around to reflect what's hidden deep inside of everyone's subconscious/unconscious minds. And everyone's otherworld would bleed and leak into each others.

(Example using my own characters. Alessa's afraid of fire, so her otherworld would contain areas of fire, and buildings might look as if though they've been burned. Flauros is afraid of being trapped so his otherworld would for example contain stocks, cages, and prisons. Alessa's otherworld would leak into Flauros's and vice versa. So Flauros would also be seeing fire, and vice versa. And that's just an example.)

Monsters would also be lurking around, common monsters from the games, or ones created from the character's psyches.

tl:dr - SH week, where things go to bizarro Hell.