Somber Knight, the Slayer

+2: Deal 1 damage to target creature or player, deal 2 damage to target dragon or player
-5: Somber Knight, the Slayer does not untap until next untap step exile all but one dragon that dragon must have the most power.
-10: Create a 7/4 Metal Bull with trample. Somber Knight, the Slayer gets haste and all dragons get -2/-2.