This is the version of this deck that got me to mythic. This is primarily a tempo deck with some "toolbox" qualities.

Playing

Goal number one is to stop our opponent from winning. Don't focus on building a board state or attacking, that will happen as a side effect. That being said, don't miss opportunities to get in for damage.

Opening

The best opening is to have an answer for their first play and continue to gain tempo from there. For example, Spell Queller on their first or second spell, or Reflector Mage a creature.

Next to that, Charming Prince or Fblthp, the Lost can help setup land drops or find key pieces for the matchup.

Finally, Elite Spellbinder can be a good first or second play to pull a key piece from their hand. Try to take away the resources they need, e.g. if their low on lands, take their card draw/selection. Viewing their hand can also help determine what should be targeted with Spell Queller later.

If any of those aren't an option, either mulligan or pray to the RNG for a good shuffle.

When beginning without knowing the matchup, lean towards assuming they'll have something for Spell Queller or using Charming Prince to setup your next play. A removal spell on Charming Prince is generally good for you.

Midgame

This is where Collected Company and Kayla's Reconstruction really shine. In most matchups, you'll want to play Collected Company in response to an opponent's spell. However, be cognizant of how many Spell Quellers are in the deck. If you're more likely to hit Reflector Mage or Skyclave Apparition, it's best to let it resovle before firing off CoCo.

For Kayla's Reconstruction, you'll want at least 5 mana for this to get the same value as CoCo. There's probably an argument for not casting it above X=3 as getting 4 hits is less likely, but just go for it if you have nothing else to do with your mana.

Playing Kayla's Reconstruction requires good timing as it usually leaves you tapped out. If sweepers are a possibility, it may be best to wait or hope you hit Elite Spellbinder. KR can also be a good post-sweeper play.

Card Choices

Mainboard

Staples

These spells are the core of the deck. The creatures will generally be the best hits with CoCo or KR and what you'll use to control the tempo of the game.

• Spell Queller: Probably the best spell in the deck. Whether it's being cast from hand or hit off Collected Company, the tempo swing is what this deck is all about. It pairs amazingly with Drannith Magistrate. I've played several matches with them both in play where my opponent destroys Queller and then realizing they can't cast the spell under it because it's not from hand. Be careful using this with Eldrazi Displacer! Make sure you have "auto order triggers" turned off so you can decide when the spell on the stack is exiled and the currently exiled spell gets cast. This is easy to get wrong and has lost me at least one game.
• Reflector Mage: This is another card that can get you ahead on tempo. When bouncing opposing creatures with ETBs, be sure you're ready for the next turn it is cast. Following this up with Elite Spellbinder is sometimes redundant, but it depends on the situation; it can be the correct play. This is one of the best blink targets. Pay attention to the wording on the trigger: "[...] until your next turn." So, if you bounce something on your opponent's turn, it's just a normal bounce effect. They'll still get to cast it again on their next turn.
• Skyclave Apparition: As the primary removal spell in the deck, it can be tricky to use since it gives a token to the opponent. When blinking with Eldrazi Displacer or Charming Prince, be mindful of what you're exiling first so your opponent gets the smallest token possible. Also, in that case and when you know it will be removed, remember that it's often better to give the opponent a vanilla token than let them keep a creature with abilities.
• Collected Company: We play this deck to cast this card. When you hit, the early/mid-game value is unmatched; essentially getting a two mana discount on two creatures while giving them flash. Be mindful of what creatures are not chosing because they go to the bottom of your library. This will affect the probability of what you'll hit next time. If you just put three Quellers to the bottom, maybe don't cast another CoCo hoping to get the last one unless its a hit or lose situation. Speaking of Spell Queller, if you're likely to hit one, don't hesitate to cast this in response to a spell that you don't want to resolve.
• Kayla's Transformation: If expecting interaction, try to get the opponent tapped out before casting this one. Occasionally, I'll run a CoCo into a counterspell just so I can cast this for X=3 or more on my turn. Casting for X=1 is basically a desperation play and should be avoided unless absolutely necessary. Casting for X=4 or more should be rare because you're unlikely to get that many hits. I haven't done the math, but annecdotally this makes sense. This is one of the best post-sweeper plays. If your board is getting wiped, save this for those situations. In most situations, you won't want to cast this just to get more creatures on the board; you'll want to either be trying to hit something specific or use it to rebuild. Also, if you've cast this and are deciding if you should choose Spell Queller or send it to the bottom, choose it and put it into play. Evasive threats win more games and you can hope for a Displacer down the road.

Support

These creatures are either getting you to your staples or making them better.

• Charming Prince: A nice utility creature. Generally, you're going to be using the scry or blink modes. Don't forget that the blink effect returns on the next end step as this can be relevant. Sometimes it's nice to blink on the end step to delay the ETB of the target creature. This can cause the opponent to play differently knowing there's a Reflector Mage or Skyclave Apparition returning on the next end step.
• Eldrazi Displacer: This is such a great utility creature, but you need the mana for it (specifically, colorless mana). It's probably best to play when you have mana for at least one activation, but its stats are also nice and will sometimes make a good blocker or trade. Just about every other creature has an ETB trigger, so targets are plentiful. Don't forget they return tapped! This means it can also be used to neutralize any opposing blockers. If you have mana for two activations, you can do some tricks targeting Spell Queller or Skyclave Apparition by blinking again in response to the first ETB trigger; this leaves the first ETB's target exiled forever. Counter wars with Spell Queller and Displacer are fun. :D
• Fblthp, the Lost: I wasn't sold on this card at first, but in practice it's been great. Casting it from hand is not ideal, but decent. It can be a good target for Eldrazi Displacer, but the main reason for it is playing it from your library mid to late game. Two cards can swing things in a better direction when your hand size is dwindling.
• Grazilaxx, Illithid Scholar: Both triggers are great, but this card attracts removal so play it when you can get some value. The best scenario versus blockers is when you've established a board with a flier that can connect and an ETB creature that you want to pick up; you get both triggers, netting two cards by sacrificing a bit of board presence. In general, don't attack with this creature when it can be blocked. You will get a chance to pick it up, but then the draw trigger won't happen.
• Glasspoll Mimic: It's a land only when you absolutely need it, but I would keep a two land hand that includes this as the third. I think the utility here is obvious: theres a creature on the board that you want to trigger again. Keep in mind that the creature has to be in play before this enters; i.e. if you play CoCo or KR on an empty board, there's nothing available to copy and it will enter as a 0/0.

Situational

These are amazing in some matchups, but sometimes they will feel vanilla. When that happens, side them out on game 2.

• Tomik, Distinguished Advokist: Best on turn two against decks trying to untap and/or enchant their lands. Will also shut down Field of Ruin versus your lands.
• Drannith Magistrate: Even with its underwhelming stats, there are enough decks that want to cast spells from other zones for it to be worth the slots. This attacks Adventures, Foretell, Flashback, Aetherworks Marvel, and the like. Plus, the synergy with Spell Queller and Elite Spellbinder can be incredibly powerful. You can lock an opponent out of the game with this by blinking Elite Spellbinder with Eldrazi Displacer on their draw step.
• Knight of Autumn: Another great blink target and can be the hate needed against certain matchups. It's necessary against Shark Typhoon and Skysovereign, Consul Flagship since Skyclave Apparition is useless against them.
• Citywide Bust: This gets rid of anything too big for the staples to handle and it doesn't touch any of your creatures. There may be a better choice here, but it's been clutch on more than one occasion.
• Field of Ruin: Those pesky creature lands will kill you! This deals with one of them. Do be mindful of how many basics you have left and that it shuffles your library, so anything put to the bottom previously will be randomized. One note about Hall of the Storm Giants: destroy it in response to activation or when they're tapped out; if they have mana to activate and you try to destroy it, it gains ward 3 and potentially counters the ability.

Sideboard

• Selfless Spirit: Great when expecting sweepers or decks with a small amount of spot removal. It's a toss-up versus decks focused on spot removal. Don't play on turn two unless you want it to eat a removal spell. If it's being destroyed or exiled, always activate its ability. This can either counter a side-effect of the removal spell, or protect the rest of your board for the turn.
• Remorseful Cleric: Pretty obvious one here. If they're using the graveyard, bring it in. One interesting matchup where this is useful is versus Rogues which benefits off your graveyard being full; i.e. exile your own graveyard.
• Tomik, Distinguished Advokist: Mostly to slow down Mono-Green Ramp, but it can also be useful versus decks using Ossification.
• Soulless Jailer: For the reanimator matchups or other decks making heavy use of noncreature spells in the graveyard, e.g. Mono-Green Ramp, Izzet Phoenix.
• Archon of Emeria: This rarely affects our game plan, so bring it in against decks that are non-basic heavy or spellslingers.
• Guardian of Faith: A decent body that can be hit with CoCo that protects against sweepers or other removal. Best response to Farewell.
• Knight of Autumn: When you need to destroy that pesky enchantment. Also good when you need to gain life.
• Reidane, God of the Worthy: Decent versus control or others casting big noncreature spells. The option to play the flipside is also worth considering.
• Prowling Serpopard: Stop countering my stuff! Nice stats, too.
• Authority of the Consuls: Versus aggro, especially Mono-Red. Also, this shuts down the Izzet Creativity combo with The Locust God (for a turn at least).
• Fateful Absence: Essential for dealing with Elesh Norn, Mother of Machines, but useful versus other big creatures and planeswalkers.
• Dovin's Veto: Can be clutch versus combo and control.

Matchups

Tough Matchups

• RB Midrange: Winnable, but very tough.
• U Tempo: Just concede. :D Once they get ahead, it's basically impossible to catch up. If you are wondering if they have a counterspell, they do. Having said that, I haven't played this again since adding Prowling Sepopard; maybe that swings it a bit.
• UW Control: Counterspells, sweepers, and haymakers; everything our deck has issues with. Very unlikely to win. Board out Skyclave Apparition.

50/50 Matchups

• Mono-Green Ramp: Winnable, but things need to line up right. Things seem to work out about half the time.
• Mono-Black: Discard can ruin our plans if they choose correctly. Plus, they have loads of spot removal.