Whenever a creature you control attacks, it phases out at end of combat. (While it's phased out, it's treated as though it doesn't exist. It phases in before you untap during your next untap step.)
Whenever any creature you control attacks, it phases out at end of combat.
"I don't like to speak ill of 'walkers . . . but just what did Teferi think he was doing?"
—Ertai, wizard adept
