This might be the most viable PDH mill deck so far, outside of infinite combos, just because of the unique interaction between our commander and having any number of petitioners in our deck. It basically turns Wood Sage's ability into a free draw or two every turn by always naming Persistent Petitioners, while also letting us fill our grave with incidental value like flashback cards. This huge source of card advantage lets you run fewer petitioners and more supplemental cards, while still getting a steady stream of your key creature. Wood Sage also shines in this role because he is cheap to recast, so your opponents removing him won't slow you down very much. Our sage's only real weakness is auras that won't let him untap or keep him from activating abilities (which we can get around if Silent Departure is in our hand or graveyard).
This deck plays extremely linearly. Draw stupid amounts of petitioners and play them as quickly as possible. Chump block where necessary. Mill everyone until they're dead (but target them one at a time). Most of your important decision making will revolve around when to use flashback cards, who to target first with mill, and when to block or not. Go-wide strategies will have a hard time getting through our wall of blockers, and we'll have blockers very consistently from turn 3 on, so aggro isn't too much of a worry. This leaves flying/unblockable creatures, large green things with trample, board wipes like Crypt Rats, and infinite combos as the main threats to the deck. I've only come up against Crypt Rats once in testing so far, and was able to recover VERY quickly by playing 4 more petitioners the next turn. That kind of board wipe should only knock this deck out of the game if it's repeatable.
For our supplemental cards, we have a decent amount of card draw from flashback spells like Deep Analysis and Think Twice, as well as traditional card draw sources like Rhystic Study, Distant Melody, and Treasure Cruise. We also have some card filtering available from the grave in Oona's Grace. Our tutor suite includes Trinket Mage, as well as the transmute cards for CMCs 1, 2, and 3. These let us search for a fog effect (Moment's Peace), grave hate to use on our opponents (Tormod's Crypt), defensive equipment (Slagwurm Armor), ways to shuffle our grave into our library in case we are also getting milled (Feldon's Cane), or just for draw sources (Rhystic Study). We also have a few ways, like Pulse of Murasa and Wildwood Rebirth, to get cards back from the grave if we mill something important. Our last supplemental cards are our ways to untap Wood Sage, which just allow us to dig through our deck faster.
There is also an infinite mana combo in the deck, although it is purely by accident and is limited in its usefulness. If you put Freed from the Real on Tidewater Minion and have out Simic Growth Chamber (tutorable with Expedition Map), then you can get infinite green mana. The only way I see this being useful is to play out your flashback cards and hand as quickly as your islands will allow you to.
