I was considering having another world's Gods attempt to invade this one.
Interesting contrasts, possible battles, people are affected, possible new gods if someone defects...
“She'd become a governess. It was one of the few jobs a known lady could do. And she'd taken to it well. She'd sworn that if she did indeed ever find herself dancing on rooftops with chimney sweeps she'd beat herself to death with her own umbrella.”
― Hogfather