Vraska, Betrayals Sting Proliferate as a loyalty ability is already an engine in and of itself, and Vraska, Betrayal's Sting offers much more than that
you may play the exiled card without paying its mana cost if the total power of creatures you control is 10 or greater
When Mystic Sanctuary enters untapped, you get to take an instant or sorcery card from your graveyard and put it on top of your deck
I never really see this card in decks, but I think if you have any sort of scooping effect like AZ, Super Scoop Up, or Seeker, you should always play this card
Optional sanding at edges if desired
Harvester of Misery's second ability affects only other creatures that are on the battlefield at the time it resolves