A floating city hovers over the capital, seemingly appearing out of nowhere. Its spires are blinking in the morning sun, revealing alien architecture. What will happen next? Rumours spread like wildfire that this is the ancient city that once stood at this very spot. Mystics proclaim that it will take root here once again, crushing the capital under it. Somebody needs to get up there and investigate.
A circus is in town and while parading down the main street the animals suddenly break free from the cages. After surviving and assisting during the breakout the PCs are hired to help with the investigation. Who did this and why?
Believable magic, like ordinary physicis, operates according to some invariable laws that always result in some kind of cost or "bounce back". The grater the magic, the more it should cost the character physically, emotionally, and spiritually.