Light Horn Mutant, Dangerous Horn

:When this unit is placed on or , choose a card from your hand, and you may reveal it. If neither that card nor your vanguard is a card with "Darkface" in its card name, this unit gets -5000 until end of turn. :If you have a grade 4 vanguard with "Darkface" in its card name, and the number of your opponent's rear-guards is one or less, this unit gets +6000.