This list was made through the collaberative efforts of user: WizardAdpet, Strix, ka0s, KOKO, and Hissp. If you would like to discuss this deck or other Yuriko builds please join the Official Yuriko cEDH Discord!

https://discord.gg/pjZyNP5
Description
Yuriko is an interactive commander whose ability allows us to circumvent the commander tax, making her hard to disrupt for too long. She also functions as a card advantage engine and even a win condition if left unopposed for too long. In the past, Yuriko was a disruptive general due to the lack of immediate win conditions. Since the release of Thassa's Oracle, Yuriko has been able to run Oracle/Consult lines in addition to Doomsday with great efficiency, while still maintaining the inevitable damage win-con, making her a very adaptive general.
Why play Yuriko over other Commanders?
Combat is a legitimate win condition, meaning decks that want to drag the game out help us, and we can provide a very real clock on opponents. With Yuriko in play, you'll always have a win condition to build towards, while still giving you an emergency option of Oracle Consult.
Our entire gameplan is built around acquiring card advantage until we are able to combo. Card draw is the best thing in magic and we get to play a reverse Dark Confidant with additional upside once we start getting more ninjas into play—Yuriko can quickly snowball out of control, especially with our two favorite ninjutsu cards from modern horizons: Ingenious Infiltrator and Mist-Syndicate Naga.
One card win-con in Doomsday with the ability to include multiple win attempts, as well as the incredibly powerful combo of Thassa's Oracle + Demonic Consultation.
We get to run some backbreaking stax pieces and are hit by almost none of them. The only common stax pieces this deck is hurt by is taxing effects such as Sphere of Resistance and nonbasic land hate like Blood Moon, and even those aren't so much crippling as they are difficult.
Our commander is very resilient to board wipes/removal. If it's not specifically "steal target creature" or Oko effects, yuriko can often bounce back from anything.
We get to include cool cards that aren't seen often at cEDH tables. Who else plays Commandeer?
Ninjas
How does this deck win?
Yuriko Triggers - The tried and true method of delivering victory with Yuriko. Use her ability to flip cards from the top of your library for damage, or abuse cards like Brainstorm and any of the top-deck tutors.
Doomsday - This is covered in detail in the "Doomsday" section.
Thassa's Oracle paired with Demonic Consulation or Tainted Pact - This is covered in the "Combo" section.
Using Sakashima's Student to copy an opponent's Dockside Extortionist - This is covered in the "Tips & Tricks" section.
Notable Exclusions
All 2cmc mana rocks: All of the 2cmc mana rocks are mana-negative and that is especially brutal in Yuriko where our turn 1 is dedicated to playing a creature, and our turn 2 is dedicated to playing Yuriko with very few exceptions.

Abjure - While it is a 1cmc counter, it slows down our deck and we lose tempo, especially if we sacrifice Yuriko. There are better 1cmc counters available that do not hinder speed.

Insidious Dreams - Insidious Dreams is a trap card. On the surface it seems tailor-made for Yuriko, when in fact, it is extremely risky and expensive. Discarding the cards is part of it's cost, so if it gets countered, it hurts twice as bad, and the payoff isn't particularly high until there's one or two additional ninjas, which requires even more investment. We are much better suited using Doomsday or other top-deck manipulation, or simply saving mana to use the spells we draw.

Mana Drain - This card is excluded in much the same way as other 2cmc counterspells. This deck is very mana intensive and traditionally does not have the mana available for 2cmc interaction, and UU is a difficult mana cost to hold up. However, we do try to maximize on the "free" and/or 1cmc interaction cards.

Notion Thief - At 4cmc this is a tough add. While it's a great card on it's own, it really shines in builds like Opus Thief. We don't run wheels so it's not nearly as efficient or needed.

Other extra turn spells - With the addition of the Oracle/Consult lines as well as Doomsday, the other extra turn spells (5 mana extra turn spells) have become obsolete. Pre-Oracle they were a great way to get in more Yuriko triggers, but we have faster and more efficient ways to win now.

Rhystic Study - This is another casualty of Yuriko being very mana-intensive. While great in most cEDH decks, it's very tough to cast and still interact at 3cmc.

Sensei's Divining Top - On the surface, the Top seems like a great fit for Yuriko, even a Doomsday pile cracker. However, it is not. It does not crack Doomsday piles efficiently as it goes right back on top of the pile that you need. Also, while the first activation is great, any subsequent activation are lackluster and do not provide enough advantage to warrant it's constant mana requirements.

Sol Ring - A quick glance at the deck will show that there are very few spells that Sol Ring can help us cast, and even fewer that we actually want to cast early that we want sol ring's help with with. Yuriko is very colored mana-intensive and Sol Ring is a wasted play in most cases. Mana Crypt gets a pass for being free while yuriko has seen an increase in the colourless costs that she wants to run.

Walker of Secret Ways and other ninjas that are not included - Yuriko looks to maximize the amount of 1cmc ninjas that it runs, as well as running a few 2cmc ninjas that have abilities which are so good that it warrants the extra cost. Unfortunately Walker is not one of them. Ninja of the Deep Hours, Sakashima's Student, and Ingenious Infiltrator are the only 2cmc ninjas that the authors feel are worth including in a Yuriko cEDH build. Additionally, Mist-Syndicate Naga has the ability to win a game by itself if left unanswered so it is our lone 3cmc ninja.

Tips & Tricks
The Dockside Loop

The Dockside Loop is a loop that can generate unbounded treasures and potentially get a win when a few simple conditions are met.
1. An opponent has a Dockside Extortionist in play
2. Sakashima's Student in hand
3. Generating a copy of Dockside must produce 5+ treasures
4. Have another Ninjutsu creature ready to activate after Student is in play. Usually this is Yuriko if she is unblocked, but if you have Skullsnatcher or Mistblade Shinobi in hand/unblocked you can preform the loop with only 4 treasures

To do this loop, attack a player with a creature and have it not be blocked. Announce Ninjutsu with Sakashima's Student. Have it enter as a copy of Dockside Extortionist, generating 5 treasures. Use 2 treasures to Ninjutsu Yuriko into play, returning the Student to your hand. Use 2 more treasures to Ninjutsu Sakashima's Student, returning Yuriko to hand or command zone. Repeat. In this example 1 treasure was generating each iteration.

Finally, if possible, have Sakashima's Student enter as a copy of a creature that can make use of infinite mana. This could be your own Spectral Sailor or one of your opponents creatures. Common examples are: Thrasios, Triton Hero, Najeela, the Blade Blossom, Urza, Lord High Artificer, Kenrith, the Returned King.

NOTE: You can do this AFTER damage has been dealt and Yuriko triggers have resolved. This is important because it means you can cast Imperial Seal (during main phase 1), Vampiric Tutor, or Lim-Dul's Vault prior to damage if you don't have Sakashima's Student in hand, reveal it from the Yuriko trigger, then proceed with the loop in the Combat Damage or End of Combat steps.

Below are the relevant rulings that allow this to happen - Explanations of rulings courtesy of deak.

702.48a Ninjutsu is an activated ability that functions only while the card with ninjutsu is in a player’s hand. “Ninjutsu [cost]” means “[Cost], Reveal this card from your hand, Return an unblocked attacking creature you control to its owner’s hand: Put this card onto the battlefield from your hand tapped and attacking.” This is relevant to timing of activation, and that the returned creature is part of the cost, so you cant respond by removing it.

702.48c A ninjutsu ability may be activated only while a creature on the battlefield is unblocked (see rule 509.1h). The creature with ninjutsu is put onto the battlefield unblocked. It will be attacking the same player or planeswalker as the creature that was returned to its owner’s hand. This specifies that the creature put onto the field is unblocked and is attacking the player. This is relevant because it means they can be ninjutsu'd out, even in the end of combat step

509.1h An attacking creature with one or more creatures declared as blockers for it becomes a blocked creature; one with no creatures declared as blockers for it becomes an unblocked creature. This remains unchanged until the creature is removed from combat, an effect says that it becomes blocked or unblocked, or the combat phase ends, whichever comes first. A creature remains blocked even if all the creatures blocking it are removed from combat.

This specifies that when a creature "becomes" unblocked or blocked and how that status stays on them until the end of combat phase

Doomsday Piles
Doomsday is a card that has terrorized magic players for many years. Before the unbanning of Protean Hulk, Doomsday was one of the premier threats of the format, and even during the Flash Hulk era it was quite relevant in a number of decks. Once more it comes to deliver wins to the enlightened, and with the conditions of Thassa's Oracle it has become almost impossible to stop except through countermagic. Doomsday piles have become greatly simplified since Oracle was printed, but the fact remains that it is all or nothing—should your opponents thwart your attempts you will die, and there's nothing you can do to turn back the clock.

Note: These piles rely on Yuriko or another ninja attacking and getting a Yuriko draw trigger. That being said you, if you cannot attack and/or have no way of getting that first card from the Doomsday pile you can still cast Doomsday and stack your pile and pass the turn and wait for your draw on the next turn. While risky it is still very doable, especially if you have interaction in hand.

Updated Doomsday Basics: Single trigger gush pile, requires BBBU: Gush, Gitaxian Probe, Lotus Petal, Thassa's Oracle, Agadeem's Awakening

Single trigger gushless pile, requires BBBU: Gitaxian Probe, Brainstorm, Thassa's Oracle, Mox Amber, Lotus Petal

Single Triger gushless pile that doesn't lose to a kill spell on oracle, requires BBBBU: Gitaxian Probe, Village Rites, Thassa's Oracle, Lotus Petal, Agadeem's Awakening

Doomsday Tricks:

The gushless pile loses to removal on oracle if you don't have extra devotion because brainstorm puts two cards back on top of the deck.
If you have extra mana, replace the mana sources in the piles with free counterspells.
Cavern of souls is a tech option if you think your opponents are sandbagging red blast or creature counterspells, replace Lotus petal with it in the piles (but don't cut lotus petal for cavern).
If you have more ninjas, you can cut draw spells for counterspells.
Though Agadeem's Awakening is included in the piles, you can remove that and include Street Wraith at the top of the pile to make them immune to multiple removal spells
Flex cards
Sidisi's Faithful - Though sacrificing Yuriko to bounce a creature is very appealing, the lack of power in this creature means that it can be difficult to use it to enable a turn 2 yuriko, and especially later in the game to attack past a wall of dorks and utility creatures.

Fallen Shinobi - This ninja costs a whopping 4 mana to ninjutsu into play. Its power is well worth the cost, but in many cedh games it simply is too slow to readily put into our deck. If your meta happens to include many slower midrange or stax decks, then this card is a powerful inclusion, but in an effort to keep this list tuned for a broader cedh meta it has been kept from the official list.

Scroll Rack - This card is an excellent way of turning all of the redundant enablers and more situational cards that you draw into throughout the game into real cards and can be used to set up damage lines with mystical tutor to double dip on the most potent burn cards. Unfortunately, it is both slow and somewhat expensive to use. To both play and use its ability requires three mana, which is a lot for a deck that tries hard to limit the amount of actual mana spent for our cards as we do, and without a way to shuffle the deck it can freezes our topdecks. If you plan on piloting the list with a much more aggressive playstyle than this isn't the card for you, but it can be a boon if you prefer to sit back and draw the game out.

Bloodchief Ascension - This black enchantment is very powerful in the lists that have an easier time turning it on. In this list, it usually becomes active the end step of the turn after you play it, and once it's online, it changes the game dramatically. It shuts down Ad Nauseam lines and Underworld Breach combos, ruins Razaketh, the Foulblooded combos, and puts a very fast clock on midrange decks, because every spell they cast puts them closer and closer to dying from every topdeck tutor we have. That being said, it is especially weak to being bounced, as once it leaves the field you will have to wait a full rotation, and while it stops many combos it doesn't stop value plays. This is an extremely powerful inclusion, but it is up to each player as to whether or not it fits their playstyle.

Jace, Wielder of Mysteries - This card can be an alternative to Agadeem's Awakening in Doomsday lines. Agadeem's provides a chance for redemption should Oracle be countered or your board wiped. Jace, however, provides an extra threat in the deck if the games go long or if Oracle is killed before you find Pact or Consultation, while also serving as a functioning value card in longer games. Jace also makes it safer to cast Pact or Consultation for value in matchups where you need the combo to kill, but also need to spend a forbidden tutor to keep up with the game.

Drown in the Loch - Universal counterspells are indeed quite powerful, and the flexibility that this card offers is quite attractive. However, Drown is extremely slow, and can often struggle to counter threats like Ad Nauseam and Smothering Tithe early in the game. If you find your meta to be high in creature-based value plays, such as Seedborn Muse or stax creatures, then Drown can be a powerful inclusion, but overall it is too slow and clunky to really serve us well.

Smoke Shroud - Providing evasion to our ninjas for no mana is quite strong, as it practically guarantees us to get triggers, and is yet another way to beat a common problem of needing to discard cards after a turn 2 Yuriko. However, it is generally not necessary and also requires either a second ninja or for the untimely death of our commander, both of which are generally outside of our control. If you want a more value-based playstyle, this card may be for you.

Mana Maze - Arcane Laboratory's younger brother, it stops some combos like Dramatic Scepter and Food Chain combos not enabled by Eternal Scourge. It is quite good at disrupting opponents who can't play around it, as well as making counterspells almost uncounterable and protecting wins with a brainstorm. However, these functions can also be used against you, so be careful when playing against other blue opponents.

Toxic Deluge - In a slower list, this is a powerful disruptive card. Many UG based midrange decks commit plenty of resources to developing their board with dorks and value creatures, while we are generally fairly light and often keep an enabler in hand. However, in the faster games of cedh, board presence often has little to no impact.

Damping Sphere - a powerful hate piece against storm and turbo naus decks, as well as shutting off Food Chain, Gaea's Cradle, and Iso/Rev combos.

Whether you want to add some of these cards to your deck, or your own special spice, you might find yourself struggling to figure out which cards to cut. Two of the easiest cards to cut from the list are Azra Smokeshaper and Ninja of the Deep Hours. They're both quite good, as 2cmc card advantage engines often are, but they are not in the same bracket as the rest of the ninjas, and merely serve as extra value.