The Mill Shell is perhaps the most simple part of the deck, requiring perhaps the least thinking in terms of the linear path of its strategy. Like Burn, Mill always aims to hit a single, particular resource and remove it as fast as possible. They key cards here are the staples
Mind Funeral and
Glimpse the Unthinkable. They both can be played on Turns 3 and hit a hefty amount of cards under most circumstances. Thanks to the meta of fetch lands,
Mind Funeral has, generally speaking, gone up in terms of raw value, though always retains significantly more strength towards the late game, where there are less lands sitting in the deck. This makes the only choice in the Mill shell a simple one: Do you hit the opponent and try to starve them out of mana? Or do you try and take out the most cards possible in the deck at the time? Depending on which way you lean, you'll want to play either of the two staples.
The third staple in the Mill shell is the bomb of the bunch. Archive Trap is something I would argue is one of the most valuable Mill spells in print, strictly because of its ability to drop on zero, furthered in this deck if one can reduce its cost to two mana, where it ekes out in value over Glimpse the Unthinkable. It also offers the deck's only OTK, which can be earned in one of two ways.
Opening Hand: 4xArchive Trap and preferably 1xGhost QuarterT1: Opponent plays fetch land. Upon resolution, drop the four of Archive Trap. Alternatively, a T1 Ghost Quarter into one of their lands, with a four of trap means death on search. If they don't search, you've reset the board, presuming there were no spells cast. Due to the likelihood of either of these occuring, I would not ever rely on this, instead opting for other Mill routes or Bad Beats.