Grimrock

I was wondering if it is possible to make a fireball that shoot from the ceiling down to the floor?
And how would you create such a spell?

I have not tried this yet, but within Fireball.LUA there is a Gravity property (default setting is 0,0,0) that may be worth exploring to achieve this.

Making a projectile and giving it a horizontally velocity of 0 and falling velocity of [whatever speed you want] should work.