If some (but not all) of the targets become illegal, the original division of damage still applies, but no damage is dealt to illegal targets. If all targets become illegal, Deft Dismissal doesn’t resolve.
Deft Dismissal deals 3 damage divided as you choose among one, two, or three target attacking or blocking creatures.
You choose how many targets Deft Dismissal has and how the damage is divided as you cast the spell. Each target must receive at least 1 damage.
