Bolt Bend

You don't choose the new target for the spell or ability until Bolt Bend resolves. You must change the target if possible. However, you can't change the target to an illegal target. If there are no legal targets to choose from, the target isn't changed. It doesn't matter if the original target has somehow become illegal itself.

If a spell or ability targets the same player or object multiple times, you can't target it with Bolt Bend.

Once you've cast Bolt Bend, losing control of all creatures with power 4 or greater won't affect the spell or cause you to pay more mana.