Destroy target creature. A creature destroyed this way can't be regenerated.
Overload {2}{W}{W} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")
Because a spell with overload doesn't target when its overload cost is paid, it may affect permanents with hexproof or with protection from the appropriate color.
Casting a spell with overload doesn't change that spell's mana cost or mana value. You just pay the overload cost instead.
Effects that cause you to pay more or less for a spell will cause you to pay that much more or less while casting it for its overload cost, too.
If you are instructed to cast a spell with overload "without paying its mana cost," you can't choose to pay its overload cost instead.
If you don't pay the overload cost of a spell, that spell will have a single target. If you pay the overload cost, the spell won't have any targets.
Overload doesn't change when you can cast the spell.