Spreading Flames

• WWizards of the Coast2016-07-13
  Official Ruling
  You announce how the damage will be divided as part of casting Spreading Flames. Each chosen target must receive at least 1 damage.
• WWizards of the Coast2016-07-13
  Official Ruling
  If Spreading Flames has multiple targets, and some, but not all, are illegal targets when Spreading Flames tries to resolve, Spreading Flames will still deal damage to the remaining legal targets according to the original damage division. If all the targets are illegal, the spell won’t resolve.

Rulings via Scryfall