Artificer's Hex

2013-07-01 In some rare cases, the creature the enchanted Equipment is attached to as the ability resolves isn't the same one as the one it was attached to when it triggered. In such a case, the creature the Equipment is attached to when the ability resolves is destroyed.
2013-07-01 Players can't pay an Equipment's equip cost to unattach that Equipment to stop Artificer's Hex from destroying a creature.
2013-07-01 The ability checks to see if the enchanted Equipment is attached to a creature as your upkeep begins. If it's not, the ability won't trigger at all. If it is, the ability will check again as it tries to resolve. If the enchanted Equipment isn't attached to a creature at that time, the ability won't do anything.
2013-07-01 This ability triggers at the beginning of the upkeep of the controller of Artificer's Hex, not the upkeep of the controller of the enchanted Equipment or the creature that Equipment is attached to.

mtg.wtf