Gray Merchant of Asphodel has been one of the most valuable cards in mono-black Modern decks for a very long time, and it will do just as fine in the current Standard season
Vexing Arcanix was also not really about milling, but anyone who's every played Ice Age sealed knows how often you use it to mill out people in Limited games (if they don't die to the damage first that is)
When Phage enters the battlefield, if you didnt cast it from your hand, you lose the game
Even with the price of Talent cards being volatile, the fact that this card is only spiking now is unusual
Rather, a second "reflexive" ability triggers when you exile a card this way
Chapter III allows you to destroy all Walls, effectively dealing with the Artifacts you chose in chapter I for good