The deck and article were designed and written by DOGGERTQBONES

https://mtgazone.com/azorius-yorion-blink-deck-guide/

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Card Choices

Companion – Yorion Sky Nomad: Yorion is one of the three companions to survive the rules change in Standard, but is by far the best of them all. The ability to blink as many things as you want is ridiculously powerful and the restriction is hardly one at all considering mill to be a popular deck in the format!

4 Charming Prince: As I said in the Orzhov Yorion article, this handsome devil is one of the best cards in your deck. The ability to constantly loop Yorion is one of the engines that makes this deck so hard to out-grind, and this is one of the ways to make that happen. Furthermore, you can just play him early as a roadblock, to help smooth your hand, or accrue additional value by blinking a non-Yorion target.

3 Barrin, Tolarian Archmage: This can function as double duty in a lot of matchups. The most obvious application is to bounce opposing creatures (or Skyclave Apparition tokens you gave your opponent) and that’s more than fine. However, you can also bounce your Yorions or other ETB creatures to accrue even more value out of them. This is one of the harder cards to use in the deck so use it wisely.

4 Skyclave Apparition: One of the best white cards in Standard right now. The ability to answer ANY permanent that’s 4 CMC or less makes this extremely powerful. Furthermore, this combines super well with Glass Casket and Yorion as you can blink both, exile the token you just gave them with Glass Casket, and exile something else! 

4 Solemn Simulacrum: I love Solemn Simulacrum. I don’t know what about him is so appealing to me, maybe it’s my EDH player roots. However, ramping for a land is really powerful in this strategy as the deck is extremely mana hungry. Furthermore, this is a great bridge spell against fast decks to help close out the game quickly if needed. 

1 Thassa, Deep-Dwelling: I see a lot of UW lists playing either 0 or 3, but I think one is the perfect number. Blinking any creature in your deck once is reasonable value, but being able to do it continuously is very powerful. Also the games where you get this and Yorion out, so many triggers. I like 1 as every additional copy is pretty bad beyond having extras in case of ECD, but generally ECD has to go after your Yorions anyway.

3 Yorion, Sky Nomad: It’s the best card in your deck, of course you want to play 4. Blink all your stuff and win the game.

3 Dream Trawler: This is relatively newer tech for UW Yorion. Although it doesn’t really fit in the deck’s general gameplan, it’s just a powerful card that’s extremely hard to answer outside of board wipes. However, with wrath effects being at an all time low, it’s time for Dream Trawler to shine. Furthermore, some strategies like GW Yorion functionally can’t beat this card without a specific sideboard answer.

4 Emeria’s Call: In BW Yorion I only played 3, and I recently learned that was definitely a mistake. This is a Bolt Plains or a Broodmate Dragon that gives the rest of your team indestructible. I’ve even had games where I cast this into a Shatter the Sky for a build your own Plague Wind. I try to hold these as long as possible since chaining multiple copies of Emeria’s Call can kill your opponent extremely quickly.

4 Glass Casket: Early removal and strong synergy with Skyclave Apparition, not much more to say.

4 Mazemind Tome: I never thought this card would see so much Standard play, but here we are. Good for smoothing draws early, drawing extra cards late, and life gain in a pinch. Try to keep these on 3 so you can blink them with Yorion to do it all again!

4 Omen of the Sea: Probably the biggest pull to being a Blue Yorion deck (maybe besides the sideboard cards). Having a card that draws cards in a Yorion deck is extremely important. Furthermore, this is a cheap and non-risky play unlike other options like Llanowar Visionary which can be easily killed or Treacherous Blessing which can kill you.

4 The Birth of Meletis: One of the best anti-aggro tools in Standard. Wall of Omens was excellent when it was Standard legal, and this card is excellent now. It doesn’t synergize the best with Yorion nor is it good late, but it’s the best turn 2 play in the deck.

4 Omen of the Sun: This deck just really hates aggro decks, doesn’t it? Omen of the Sun buys you so much time so you can work your way up to your expensive spells. Furthermore, the obvious strong synergy with Yorion is really what we’re after here.

4 Elspeth Conquers Death: The reason to play white in your Yorion deck instead of something like Dimir; this is one of the best cards in Standard and synergizes with Yorion extremely well. Exiling your opponent’s best card and recurring something of yours is just an insanely powerful effect. Small tip with this card, if you have a Dream Trawler out and nothing to get back, you can use Dream Trawler’s protection ability to discard a card and get a free permanent back!

30 Lands

SIDEBOARD

1 Giant Killer: A relatively versatile card in this format. This isn’t amazing in any one place, but is solid against most of the popular strategies in Standard right now. This can kill an important creature, then sit back to tap your opponent’s stuff. This is also important in case Dream Trawler becomes more popular as this is a great answer to it (the creature half, not the adventure half which doesn’t work as often.)

3 Mystical Dispute: This is one of the best sideboard cards ever, trailing only behind Veil of Summer. May as well play them if you can. Obviously very strong in the mirror.

2 Whirlwind Denial: I play this mostly for the blowout potential with Yorion’s SECOND trigger. You can let the Yorion player exile their board, then when the trigger to bring everything back happens, you can counter that and exile most of their board! I got this to work in the mirror already and I easily rode the game to victory after doing so.

2 Neutralize: Good against slow decks and the mirror. Hard counterspells are always nice.

4 Shatter the Sky: Even with all our anti-creature cards, sometimes you just need 4 more.

1 Dream Trawler: This card is excellent against some matchups and quite strong in the mirror as well. Having a high threat density is always helpful if decks start targeting this one with more counterspells and the like. Dream Trawler’s ability to win the game by itself is extremely useful.