Teleportal

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 with overload, that spell will have a single target. If you pay the overload cost, the spell won't have any targets.

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.