War Tubas

War Tuba's enters the battlefield with 7
advancement counters on it.
{1}: Put an advancement counter on War Tubas. Activate only as a sorcery and once per turn.
{t}: Roll a d20. If your roll is less than the amount
of advancement counters on War Tubas, blocking creatures you control gain first strike until end of
turn.
With good hearing and trigonometry, these large
aircraft detection devices could give you the location
and altitude of an approching aircraft.