Azor, the Lawbringer

Oracle Text
Flying
When Azor, the Lawbringer enters the battlefield, each opponent can't cast instant or sorcery spells during that player's next turn.
Whenever Azor attacks, you may pay
. If you do, you gain X life and draw X cards.Card Rulings
1/19/2018 If multiple effects say that an opponent can’t cast instant or sorcery spells during that player’s next turn, they all apply to the same turn.
This has interesting implications. Did Azor call Jace to Ixalan for some purpose?
That said, the Sphinx's Revelation ability is not as good as the original spell, since the original spell was 99% cast at the opponent's end of turn. When is it safe to use the ability? You're looking at needing 8+ mana to safely keep enough mana open to counter stuff.