Decree of the Vampire Lords

Convoke Vampires (Your Vampires can help cast this spell. Each Vampire you tap while casting this spell pays for {1} or one mana of that Vampire's color.)
If six or more Vampires helped to cast this spell, it has split second. (As long as this spell is on the stack, players can't cast spells or activate abilities that aren't mana abilities.)
Target player's life total becomes 10.