Combo

You probably know the combo, using Prime Speaker Vannifar to climb up the CMC ladder to get Nightmare Shepherd then untapping Vanny to combo drain with Gray Merchant of Asphodel. With the amount of recursion in the deck (Fauna Shaman, Neoform, Spark Double, Find // Finality), we can regularly win on turn 4 or 5.

Turn 1: Land and mana dork (either Gilded Goose or Llanowar Elves).

Turn 2: Land and whatever (play a 3CMC creature if you don't have Vannifar in hand).

Turn 3: Land and slam Vannifar or use Neoform to fetch her out. Then pray she doesn't get removed.

Turn 4: Land and sack mana dork to Vanny fetching a Corridor Monitor, untap Vanny, sack Monitor to Vanny fetching a Hyrax Tower Scout, untap Vanny, sack Scout to Vanny fetching a Nightmare Shepherd. Play either Monitor or Scout from hand to untap Vanny or use Find //Finality to get a copy from your graveyard and then play it. From here, the combo diverts off into two paths:

Turn 4 cont. (a): If you untapped Vanny with a Monitor, sack Monitor to Vanny fetching a Woe Strider. Nightmare Shepherd's ability will trigger creating a monitor token and untapping Vanny. Sack Monitor token to Vanny fetching a Scout, untap Vanny, sack goat token to Vanny fetching a mana dork, use Strider's ability to sack Scout (the scry doesn't matter), Shepherd creates a Scout token, untap Vanny, sack mana dork to Vanny fetching a Monitor, untap Vanny, Shepherd makes a mana dork token, sack mana dork token to Vanny fetching another Monitor, untap Vanny, sack Scout token to Vanny fetching another Shepherd, use Strider's ability to sack Monitor, Shepherd creates Monitor token, untap Vanny, sack Monitor token to Vanny fetching another Scout, untap Vanny, sack Shepherd to Vanny fetching a Gray Merchant of Asphodel, the other Shepherd creates a Shepherd token, use Strider's ability to sack Monitor, Shepherd creates Monitor token, untap Vanny, sack the other non-token Shepherd to Vanny fetching another Gary. Sack a Gary to Strider's ability, Shepherd token creates a Gary token. Sack the other non-token Gary to Strider's ability, Shepherd token creates a Gary token. By this point, Gary should have drained your opponent for lethal.

Turn 4 cont. (b): If you untapped Vanny with a Scout, sack Scout to Vanny fetching a Spark Double, Shepherd creates a Scout token, untap Vanny, have Spark Double enter as copy of Scout token (the untap trigger doesn't matter). Sack Scout token to Vanny to fetch another Spark Double entering as a copy of the other Spark Double Scout, untap Vanny. Sack a Spark Double Scout to Vanny fetching another Shepherd, Shepherd creates a Spark Double Scout token, untap Vanny. Sack a Spark Double Scout token to Vanny fetching a Cavalier of Night, Cavalier's ability triggers letting you sack the non-token Spark Double Scout (you can kill an opponent's creature if you want), Shepherd creates another Spark Double Scout token, untap Vanny. Sack Cavalier to Vanny fetching a Muldrotha, the Gravetide, Cavalier's ability triggers allowing you grab a Monitor from your graveyard, untap Vanny. Sack Monitor to Vanny fetching a Woe Strider, Shepherd creates a Monitor token, untap Vanny, sack Monitor token to Vanny fetching a Scout, untap Vanny, sack a Shepherd to Vanny fetching a Gray Merchant of Asphodel, the other Shepherd creates a Shepherd token, use Strider's ability to sack Scout (scry doesn't matter), Shepherd creates a Scout token, untap Vanny, sack non-token Shepherd to Vanny fetching another Gary, Shepherd creates another Shepherd token, sack Gary to Strider, Shepherd creates a Gary token, sack non-token Gary to Strider, Shepherd creates another Gary token. By this point, Gary should have drained your opponent for lethal.

Notes

1) We are all in on the combo, that should be your number 1 priority. Mulligan until you get at least two combo pieces in hand (Vanny [or a way to get her], an untapper creature, and a mana dork). I will usually stop at 4 cards in hand, but you can technically combo off from as little as 3.

2) If you can't fully combo but you can still fetch with Vanny or Neoform, try to get to Muldrotha and overwhelm your opponent. If you can't fetch at all (no Vanny or a Grafdigger's Cage type effect), try to beat down with Strider and Shepherd.

3) We have a selection of one-of's in the deck for a reason: fetch a Paradise Druid when you need more mana to set up getting Vanny on the field, fetch a Leyline Prowler when you're having mana trouble and want to set up or you need the lifelink and/or deathtouch to survive a couple turns and combo off, fetch a Ravenous Chupacabra to deal with a creature that's about to kill you or that is preventing your combo (Soul Warden is a good example, we can technically combo off but if our opponent has two of them the lifegain will be too much to overcome), fetch Cavalier for more removal, and fetch Muldrotha for some graveyard recursion in the late-game.

4) Control is our absolute worst matchup. In Bo1, try and wait for Teferi, Time Raveler to come down and -3 before you play Vanny. Woe Strider is hard for them to deal with; prioritize escaping it and beating down. In Bo3, if you can't combo off early or they remove Vanny game one, scoop and side out Vanny for another payoff and play the beatdown plan. They'll most likely prioritize single removal spells, counters, Meddling Mage effects, and graveyard hate, siding out sweepers and Birth of Meletis-like effects.

5) I didn't include a sideboard here because this list is for Bo1, but a typical board would include one-of creature answers to common problems. Massacre Wurm for a sweeper, Body Double for more recursion, Dream Eater for tempo, Harvester of Souls and Soul of the Harvest can draw your whole deck and may combo well with Thassa's Oracle, Elder Gargaroth can establish a board, gain life, and draw, Thragtusk combos especially well with Nightmare Shepherd, Carnage Tyrant is really hard for control to deal with, Tolsimir, Friend to Wolves and Trostani Discordant can both gain you life and give you board presence, Brokkos, Apex of Forever is more graveyard recursion similar to Woe Strider, Platinum Angel can just win you the game if your opponent can't deal with it, Garna, the Bloodflame enables haste on all of your creatures and may let you untap Vanny, Meteor Golem for hard-to-deal with permanents, Reclamation Sage for artifact and enchantment hate, Scavenging Ooze for graveyard hate, and Meddling Mage for hard to deal with combo decks. Trying to protect Vanny with counterspells or whatever is a fool's errand; if a control deck wants to remove it, they will. Be proactive in your sideboarding.

6) Running Yorion, Sky Nomad as our companion is an option. We're in the right color and it gives us more room to fit more combo pieces and answers to common meta decks. In testing tho, I found my opening hands were a lot less consistent than the non-Yorion version. Experiment with it, it's very close to being a better inclusion.

That's it. I'd love to hear any suggestions for improving the deck! It has seriously become one of my favorites of all time. Stay safe!