Imposter's Inoculation

Destroy target creature with power 0. If that creature isn’t destroyed by this spell, put a
-1/-0 counter on it instead. If that creature
dies this way, create a 1/1 Celestial Emissary creature token with hexproof, flying and islandwalk and if so, then, at the beginning of
your next upkeep, if Imposter’s Inoculation is
in your graveyard, return it to your hand.