Kiora's Dismissal

If all of the spell's targets are illegal when the spell tries to resolve, it won't resolve and none of its effects will happen. If one or more of its targets are legal when it tries to resolve, the spell will resolve and affect only those legal targets. It will have no effect on any illegal targets.

The mana cost and mana value of strive spells don't change no matter how many targets they have. Strive abilities affect only what you pay.

If a spell or ability allows you to cast a strive spell without paying its mana cost, you must pay the additional costs for any targets beyond the first.