Two main engines in this deck:
1) Ghost quarter and crabs for landfall mill.
Crabs and landfall present an early and ever present threat. Serve to mill as well as draw out opponent's removal early to protect the mill engine in later turns as it takes a few to get the pieces in place. When able (ideally with multiple crabs on the field, assuming they survive) use ghost quarter to target Oboro and tap Oboro for mana and return it to your hand. Ghost Quarter's land search effect still triggers, so you get another basic land (which you can still tap for mana this turn), then play Oboro again. That's two land entering in one turn for 0 net mana cost, equaling 6 mill per crab, up to 24 total with 4 crabs. Can repeat with each Ghost quarter.
2) Sphinx's tutelage and painter's servant for draw mill.
Painter's servant ensures that all cards, including colorless, meet Sphinx's color criteria for repeat milling.
Various draw combos serve to assemble the pieces and feed the Sphinx engine:
1) Teferi's puzzle box is the main catalyst. It helps to cycle through your deck to assemble the necessary pieces of the engine, after which it directly feeds the Sphinxes. Combined with notion thief, it means you draw even more cards to feed the Sphinxes (which then compounds on your turn when you have to put them on the bottom and draw more yourself), and that your opponent will effectively never have a hand for the rest of the game. The effects also stack, so with more than one in play you can potentially mill an entire deck in a single turn.
2) Two chromatic stars, academy ruins, and 3 mana (conveniently provided by a gilded lotus if you get one out) provide a self contained draw loop each turn for additional milling. The stars provide draw power early on to assemble pieces. Then when the sphinx hits, with at least one in the graveyard and one in play, each turn you use the three mana to tap Academy ruins, put the Star on top of your deck, sac the other star, then play the star you drew to set it up for the following turn.
Archive and Howling Mine for additional drawing power.
Jace's phantasm for body.
Ideally mana leak on one isochron scepter and twincast on the other. Double counter power to stop just about anything, or double up on drawing or removal with twincast and thoughtcast, languish, and eye of nowhere. Jace provides some extra drawing power, as well as damage reduction, flashback (combined with twincast again for double the fun), and mill as a planeswalker.
Ideal turn order:
Against slower decks.
1 - Land, Jace's phantasm
2 - land, painter's servant
3 - land Sphinx's Tutelage
4 - Teferi's Puzzle Box (Deck goes off next turn)
5 - Notion Thief
If worried about giving opponent help with one turn of cycling their cards, Notion Thief on turn 4, Puzzle Box on turn 5, deck goes off on their turn.
Against faster decks.
1 - Land, crab (draws removal/counter)
2 - crab, Dimir aqueduct, mill 6
3 - Land, mill 6, Sphinx
4 - Mill 2+, land, Mill 6 Teferi's puzzle box (deck goes off next turn)