Best Black/Blue Flying Enchantment

[Jeroth]

What is the best Black/Blue Hour of Devastation or Ixalan card to +X+Y all flying creatures controlled. I currently have Favorable Winds which is a 1 Mana cost for +1+1 but is there anything better on the cheaper, say 3 max, Mana cost?

[ApothecaryGeist]

Favorable Winds is in Ixalan.  Just curious, how many similar effects do you figure are in standard all at once?  Also, how effecient are you looking to get?  +1/+1 global effect for a mere 2 mana is pretty darn good.  Nothing else in blue/black standard right now pumps flyers.  Fell Flagship pumps pirates.  Vanquisher's Banner (CMC 5) pumps all creatures of a chosen type; plus it draws you a card.