In multi-player games you can choose a different opposing player each time it is used.

The next time damage from the chosen source would be dealt to you this turn, that damage is dealt to the targeted creature instead. Whether it’s still a legal target is not checked at this time. However, if it’s not able to be dealt damage because it’s neither a creature nor a planeswalker, or it’s no longer on the battlefield, then the damage is not redirected and is dealt to you as normal.

As the ability resolves, you choose a damage source.

As you activate the ability, you choose an opponent, then that opponent chooses a creature for the ability to target. It doesn’t have to be a creature that opponent controls. If there are no creatures that can be targeted with the ability, it can’t be activated.