UPDATE

So, Once Upon a Time was banned, and it was really important in this deck. With it, you could play two search effects (eg. Once Upon a Time + Shimmer of Possibility) by turn 2, and be ready to pull off the Repudiate // Replicate + Lotus Field combo by turn 3 very consistently. Without it, even if you replace once upon a time with another search effect, you'll be waiting till turn 4 most of the time. That's not good enough. Even on turn three it was a little questionable, only ramping fast enough to provide a turn 4 cavalier, but on turn 4, you're not even faster than if you just hit all your land drops. And the extra two mana on turn 5 isn't getting you a lot of tempo in this deck, because all your low cost plays are search effects.

In short, this version of the deck becomes too slow without Once Upon a Time. However, I think I have a way to keep playing Cavaliers anyway.

Basically, we have to stop cheating and just play all the ramp creatures our heavy curve demands. Here's an updated decklist (https://aetherhub.com/Deck/Edit/186545)

Original Description

So here's a silly deck revolving around the fact that Lotus Field instantly gives you the color requirement for all the M20 Cavaliers, allowing you to play them all in a single deck. The strategy rolls out in stages, each one jankier than the last.

Step one is to ramp by casting the Repudiate half of Repudiate // Replicate to counter Lotus Field's ETB effect, allowing us to keep all our lands when we play it. If we're lucky we can do this as early as turn two with the help of Gilded Goose. We have Once Upon a Time, and Glowspore Shaman to help us find Lotus Field and Shimmer of Possibility to help find Repudiate // Replicate, so we have a reasonable chance of getting this to work.

In an ideal world, we follow this up with a Kiora, Behemoth Beckoner, untap the Lotus Field we used to play her, and drop one of the Cavaliers that form the core of the deck. For the next few turns we can put down a cavalier or two per turn, while we wait for Cavalier of Thorns and Glowspore Shaman to fill up our graveyard. That's when Knights' Charge comes into play.

The 11 mana it takes to play and activate Knights' Charge on the same turn is very achievable for this deck, and it's typically enough to win the game on the spot. There are two main ways to achieve this, both involving Cavalier of Flame. First, if you have red mana open, you can give all your freshly reanimated Cavaliers haste and swing in for lethal. If your opponent has too many blockers for that, then you can instead sacrifice your Cavalier of Flame to your Cavalier of Night, using Cavalier of Flame's oft-forgotten death trigger to deal damage directly to your opponent.

The Mana Base

We're a Five Color deck, and we rely heavilly on Lotus Field to make that work out for us. But since we won't have Lotus Field for the first few turns at least, our low curve plays can't be in any more colors than a normal deck. We also need to make sure we can cast Cavalier of Thorns without a Lotus Field in play, since that's one of the ways we can find a Lotus Field.

It might be better to stay in simic colors, but Glowspore Shaman is hard to pass up. It's a good early creature that can help fill our graveyard, search for Lotus Field and be brought back by Cavalier of Night.

Aside from that, we have one white source and one red source as well just in case we need them, since we often have our choice of lands with this deck.

Tips & Tricks

Between Cavalier of Thorns' and Cavalier of Dawn's and even Cavalier of Flame's on-death effects, the graveyard is a resource for this deck. Cavalier of Thorns and Glowspore Shaman's ETB abilities are the most obvious way to fill it up, but Cavalier of Flame's ETB lets you discard other Cavaliers or lands, and both Cavalier of Dawn and Cavalier of Night can kill off other Cavaliers to fuel a stronger Knights' Charge.

Be wary of Fabled Passage and your mill triggers when putting a card on the top of your library with Cavalier of Thorns or Glowspore Shaman. There's nothing worse than accidentally getting rid of a card the second you get it back from the graveyard.

If you're playing on Arena with this deck, always manually order your triggers. There's going to be a lot of times when multiple effects go off at once, and the order really matters. Here's a few examples.

• You have a Kiora, Behemoth Beckoner and Cavalier of Thorns on the board and want something back from your graveyard. You play Cavalier of Night. Ordering Kiora's trigger after Night's will mean you draw the card you get back with Thorns. This is preferable if you can play it immediatly, but if not it can be safer to draw something else and leave it on top of your library to dodge discard spells.
• When activating a Knights' Charge that will bring back any Cavalier of Thorns, always check how many cards are left in your deck. If you're runnig low, you can avoid decking out by ordering the Thorn effects after any draw effects from Kiora or Cavalier of Flame.
• If you bring back a Cavalier of Night and Cavalier of Dawn at the same time, and you're planning to target one of your own permanents with the Dawn effect, you can order it first so the Golem is available to be sacrificed to the Night.
• If you don't have quite enough lands in your graveyard for Cavalier of Flame's death effect, order the Cavalier of Dawn or Cavalier of Night ETB effect you're using to kill the Flame after any Cavalier of Thorns ETB effects so you can hopefully get some extra fuel. Also order it after any draw effects and the Cavalier of Flame ETB so you can also discard extra lands.

Be thoughtful about what color mana you're making with Lotus Field. Two Lotus Fields will pay for a Cavalier with one mana of any color left over, and what color that is can make a huge difference.

Even if you don't have enough lands in your graveyard to win the game with Cavalier of Flame's death effect, keep in mind it can still sometimes be enough to kill all your opponent's planeswalkers.

When Oko, Thief of Crowns inevitably turns one of your cavaliers into an elk, remember that copying that elk with Repudiate // Replicate still gets you a cavalier.

Don't discount the static effect on Knights' Charge. Especially against aggro, the incidentall life drain can be important.

Knights' Charge can be activated at instant speed. If you don't have enough for the instant kill, activating it at the end of your opponent's turn, or during combat, is usually better.

Kiora, Behemoth Beckoner can untap Lotus Field the turn you play it, allowing you to use its three mana with the two mana floated from the lands you sacrifice. This produces 5 mana in total, perfect for a cavalier.

If you really need Knights' Charge back, Cavalier of Dawn can target itself.

Past about turn 3, you'll want to use the Replicate half of Repudiate // Replicate instead of the Repudiate half. An extra cavalier will almost always be better than more ramp once you have at least 5 mana on the board.

Be careful when putting Lotus Field on the battlefield with Cavalier of Thorns. If you don't have two non-lotus lands to sacrifice, it will set you back significantly.

As a final note, you'll want to mulligan aggresively with this deck. If we don't get the ramp combo off early, we're going to end up sitting there doing nothing for the first 4 turns. If your hand has no chance of getting the combo off, ship it back.

Sideboarding

Honestly it's really hard to make cuts from this deck during sideboarding without ruining its consistency, so you're probbably better off in best of one. But here's my best attempt at a sideboard regardless.

Veil of Summer because discard can cripple us early game, and counterspells are bad news late game. It's also a really good answer to Murderous Rider.

Aether Gust to slow things down against Oko, Thief of Crowns, Nissa, Who Shakes the World, The Questing Beast, Skargan Helkite, and Embercleave. We sacrifice a having a more permanent answer to these cards for the flexibility and speed of Aether Gust since we can typically beat the types of decks that are running those cards in the late game.

Realm Cloaked Giant because it's a board wipe we can find with Once Upon a Time.

Pulse of Murasa is a good lifegain spell against aggro strategies, with funny niche applications against reanimator strategies if you happen to face one. Between Fabled Passage, Lotus Field, and Cavalier of Thorns we'll almost always have something we can get back from the graveyard.

Agent of Treachery Because it's a huge power play against slower decks and we have the ramp to play it. Running a couple extra Cavalier of Dawn in this slot might be a good idea as well. It's less powerful, but more synergistic.

In faster matchups you can trim a Cavalier of Flame or Knights' Charge. This weakens our endgame and our offence, but those are less important than staying alive.

Cavalier of Night can come out if your oppenent is light on creatures.

Known Issues

Graveyard hate is bad for us, but it's not the killing blow it is against other graveyard focused decks. If your opponent brings it, just cut Knights' Charge and try to outvalue them with Cavaliers. It still works pretty well.

Hushbringer is basically an instant win for our opponent. I haven't seen it played in sideboards nearly so so much as I expected, so that's good. Still, the fact remains that it shuts off our entire deck, including the only removal we have for it. If it starts seeing more play we'll need Murderous Rider or something in our sideboard to deal with it.

Wicked Wolf is very hard for us to answer. We have no exile effects, and it gets bigger than our cavaliers. Aether Gust can at least slow it down, but short of that we're going to be chump blocking it a lot.

Oko, Thief of Crowns is pretty scary, being able to turn all our cavaliers into elks, and generally being the abomination we all know him to be. He'll be banned soon, and then the Cavaliers will be free.

Final Thoughts

Honestly, this is the most fun deck I've ever built. The joy I get from watching all the triggers pile up when I activate Knights' Charge is among the most fun I've had with Magic.

It can sometimes brick out if your opponent does a good job of answering Kiora, Behemoth Beckoner. And once, in a truly tragic turn, I found myself forced to put Lotus Field onto the battlefield with Cavalier of Thorns (The ETB is not a "may" ability) when the only other land I had was another Lotus Field, resulting in a one-sided self-armageddon.

But even despite this, I still love this deck.