"Mill" is a colloquial term that originates from the card Millstone, used here to mean "putting the top cards of a player's library into his or her graveyard." For example, you could say, "In the finals of the Pro Tour Qualifier, Herbert cast Tome Scour to mill away my final five cards, dashing my chances of playing on the Pro Tour." There are many players who will play with Tome Scour in their decks
Commander Masters Collector Booster Yes, Commander Masters is great for Commander and collecting
Lier, Disciple of the Drowned Do I need to explain
Natures Will It takes aggression to properly leverage Nature's Will, but the rewards are incredible
Because its an artifact, it slots into nearly any deck, and its mana cost puts it in a fun place in your Birthing Pod / Prime Speaker Vannifar chain
Alongside this, EB02 includes 26 leader reprints from earlier sets (OP05OP08 and EB01)