You can't cast Epic Confrontation unless you choose both a creature you control and a creature you don't control as targets.
Epic Confrontation
If the creature you control is an illegal target as Epic Confrontation tries to resolve, the creature you control won't get +1/+2. If that creature is a legal target but the creature you don't control isn't, your creature will still get +1/+2. In both cases, neither creature will deal or be dealt damage.
You can't cast Epic Confrontation unless you choose both a creature you control and a creature you don't control as targets.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Wayne Reynolds
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
