Mortal Obstinacy
Enchantment — Aura
Enchant creature you control
Enchanted creature gets +1/+1.
Whenever enchanted creature deals combat damage to a player, you may sacrifice this Aura. If you do, destroy target enchantment.
Slawomir Maniak
Journey into Nyx (JOU)
• #17Rulings
If another player gains control of the enchanted creature, Mortal Obstinacy will be put into its owner's graveyard.
(wotc • 2014-04-26)
You decide whether to sacrifice Mortal Obstinacy as its triggered ability resolves. If it's not on the battlefield at that time, you can't sacrifice it and destroy the target enchantment.
(wotc • 2014-04-26)
Rulings
If another player gains control of the enchanted creature, Mortal Obstinacy will be put into its owner's graveyard.
(wotc • 2014-04-26)
You decide whether to sacrifice Mortal Obstinacy as its triggered ability resolves. If it's not on the battlefield at that time, you can't sacrifice it and destroy the target enchantment.
(wotc • 2014-04-26)