I should start by saying that I rarely post on themanadrain, but have been a daily lurker and occasional poster for at least 15 years. I don't get to test much as my work is very busy.
When Oko was spoiled a friend asked me if it was good in Vintage, and I immediately said no. He's a good player and has top 8'ed many tournaments (outside of Vintage), so when he asked me repeatedly and suggested it might be good, I listened. I decided to try and see if Oko was any good in vintage. I usually play 4c control type lists, a la Brian Kelly decks with high land counts, slightly higher mana curve and access to the best control cards across most colors, think Sylvan mentor or Kelly Oath.
I started with the 4c list I had been playing, which was a control deck running Dack Fayden, Narset, and Wrenn and Six, which helped with color fixing and an occasional Strip/Wasteland lock. My first iteration of the deck with Oko looked a lot like the RUG Planeswalker lists that just top 8'ed in Pittsburgh but 4 colors meant I could run black, which allowed for demonic tutor and assassin's trophy. I really liked assassin's trophy because it really enables the land destruction pathway, as seen in this years finals match against golos shops and for a control deck to have a card that answers any problem permanent (such as an opposing Oko out of lightning bolt range, any large creature, narset, etc) is really helpful.
When I added Oko to the deck, I realized a couple of things right away. It is a great planeswalker to fight other planeswalkers and can really control the board. It forces most opponents to over commit to the board to try and stabilize. Adding Oko also meant my planeswalker count went up to 8. I think it's important to realize that Vintage now has enough good planeswalkers to run 8-10 in a deck. This hasn't been the case in the past, and in my opinion changes the way we can build decks utilizing oath of druids since a planeswalker control list like the ones currently being played are at their best when unmolested by opposing creatures and nothing tells your opponent not to play creatures better than oath. The inherent strain placed on the opponent by decks that run 8-10 planeswalkers and oath is hard to describe, and Oko is probably the glue holding it all together. Oko strains the opponent the most of all planeswalkers as an early Oko can turn your opponents mox into a creature to trigger oath even if he was holding back creatures. If you don't have oath, Oko can take over the board with creatures forcing your opponent to play creatures, resulting in making oath live. This idea of playing a more controlling list with oath as the win condition is pretty removed from the typical combo oath strategy of turn one oath, but I think it is a viable option for RUG planeswalker like decks to at least consider. It also means that it may not be necessary or even correct to play 4 oath and 4 orchards, if oath is functioning like a mid to late game win condition rather than a primary combo. It just means that while the opponent is playing 2-3 x tarmogoyf you are playing 2-3 x oath. As a side note, Oko also works well with oath post board to remove containment priest and graffdiggers cage.
4c Planeswalker Oath
Lands/Mana
3 Misty Rainforest
4 Scalding Tarn
1 Black Lotus
1 Mox Ruby
1 Mox Sapphire
1 Mox Jet
1 Mox Emerald
1 Sol Ring
2 Volcanic Island
2 Underground Sea
3 Tropical Island
1 Strip Mine
1 Wasteland
1 Forbidden Orchard
1 The Tabernacle at Pendrell Vale
Oath Package
3 Oath of Druids
1 Emrakul, the Aeons Torn
1 Inferno Titan
2 Crop Rotation (for orchard, strip lock, mana fixing, or tabernacle)
Planeswalkers
2 Oko, Thief of Crowns
2 Narset, Parter of Veils
2 Wrenn and Six
2 Dack Fayden
Counters/Answers
4 Force of Will
1 Force of Vigor
1 Flusterstorm
1 Mental Misstep
1 Pyroblast
4 Assassin's Trophy
Draw/Tutor
1 Dig Through Time
1 Gitaxian Probe
1 Brainstorm
1 Demonic Tutor
1 Time Walk
1 Ancestral Recall
1 Ponder
1 Preordain
1 Treasure Cruise
SB: 1 Pithing Needle
SB: 1 Ashiok, Dream Render
SB: 1 Bojuka Bog
SB: 1 Veil of Summer
SB: 2 Blazing Archon
SB: 2 Forbidden Orchard
SB: 1 Oath of Druids
SB: 4 Leyline of the Void
SB: 1 Null Rod
SB: 1 Force of Vigor
I would like to make some brief comments on the card choices in the deck.
The lands/manabase is notable for a single Forbidden Orchard. As a control deck, I didn't want to play a long game and have to fight my own spirit tokens. Oko gives alternatives to activate oath and I wasn't planning on combing early. In the interest of diverse options, I run 2 crop rotations, which can find orchard but several other utility lands including strip, tabernacle, and bojuka bog from the SB. This also increases Green count for oath of vigor. I put 2 Orchards in the board for games when you need to speed up. Also, Wrenn can get back lands sacked with crop rotation, and postboard bojuka bog can be sacked to find tabernacle (for example) and then recurred with Wrenn.
The one sol ring could be the last mox to increase the chance of turn one oath, but I preferred the extra mana provided by sol ring.
Oath package
I went with 3 oath of druids since it is more of a midgame play after the opponent has been forced into playing creatures to deal with the planeswalkers. The last is in the board for games when you need to accelerate.
Emrakul is nice in that if you draw it, which occurs more often in a deck not trying to combo, it can be discarded to reshuffle. Just be sure to return a strip mine first to avoid loosing a strip lock.
Inferno titan is castable and can easily deal with Elk tokens. Blazing Archons in the board is pretty common these days for dredge, survival, etc.
The planeswalkers are pretty self-explanatory. Oko is great for board control and forcing favorable board states for oath or keeping your other planeswalkers alive. Narset is amazing and can play with Dack to occasionally force your opponent to draw 1, discard 2. Wrenn can fix mana, strip lock, replay tabernacle or bojuka bog, and go infinite turns with time walk late game, while avoiding pyroblast (much like oath). Dack can sometimes ultimate, which causes assassin's trophy to become a two-mana uncounterable control permanent, which is pretty sick.
Control package is pretty heavy on control, though I would love 1-2 more counter spell effects. Assassin's trophy is a great answer to everything (except stonecoil serpent). It can compliment strip lock or remove key permanents. The flexibility makes it invaluable in my opinion.
The draw package is pretty standard. Delve cards get turned on earlier with oath.
Anyway, I think that I will stop here. I know this was long, but i would love to hear any thoughts from people who have tried something like this or feel that this list has subtle (or glaring) weaknesses.