Necropotence was seen as a great defining feature of black, but unfortunately proved to be too strong and carried with it too much rules baggage. Yawgmoths Bargain was Mark Rosewaters attempt to make a new Necropotence that addressed both of these issues
Once a Locations Willpower is reduced to zero or less, by having Damage counters applied to it that are equal or greater than its Willpower value, the card is banished and placed in the owners discard pile
The Enchanted cards came as a total surprise
OM1 (the main set) is legal in all Arena formats , and Standard in particular that seems to be the most important reason, by far, for WotC to do Through the Omenpaths to begin with
This card also synergizes well with the noncreature spell strategy, since it will let you fix your draws each time you cast one
It was inspired by Deranged Hermit, but Vanishing 3 is much more reasonable than that