Mistveil Shinobi

Ninjutsu {2}{w}{u}
Phasing (This phases in or out before you untap
during each of your untap steps. While it's phased out,
it's treated as though it doesn't exist.)
Whenever one or more Ninja or Rogue creatures
you control attack, target nonland permanent you
don't control phases out. Then, after blockers
have been assigned, if Mistveil Shinobi is phased
out, it phases in tapped and attacking.