This deck is built primarilly around Knights' Charge. Specifically, the activated ability that lets us return all Knight cards from our graveyard to the battlefield. Now, if we're going to get our mana's worth for this we're going to need some powerful Knights. Preferably, they'll also have an immediate effect when they enter the battlefield so we can get value even if our oppenent has a wrath effect.

The best choice for this is the M20 Cavaliers. Not Cavalier of Gales though, because it's hard to get it to stay in the graveyard. And to be clear, they do give us our mana's worth. In fact, if Knights' Charge brings back even 4-5 Cavaliers, 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 (or destroy it with Cavalier of Dawn), using Cavalier of Flame's oft-forgotten death trigger to deal damage directly to your opponent

But how do we play all these Cavaliers in a single deck given their heavy color requirements? That's where Lotus Field comes in, providing the color requirement for all our cavaliers all by itself. And, by happy coincidence, Cavalier of Thorns is really good at finding Lotus Field for us.

But, even if we have the color requirements for all 4 cavaliers, that still leaves us with a very heavy curve. 13 five drops is a lot, so we need a lot of early ramp.

Being in green makes this easy. There's no shortage of cheap ramp creatures to include, and as a bonus they produce mana of any color. This gives us a backup way to cast our Cavaliers if we can't find a Lotus Field.

But that won't be enough by itself. It costs 11 mana to play and activate Knights' Charge in one turn (13 if we also want a Cavalier of Flame activation), so we need to keep ramping in the mid game if we want any hope of achieving that kind of mana.

So we keep up the pace with Cavalier of Thorns, Kiora, Behemoth Beckoner, and The Great Henge.

Kiora is perhaps our strongest ramp, allowing us to untap Lotus Field for three full mana, while also letting us draw a card for each Cavalier we play.

The Henge isn't quite as stong on ramp, but does let draw off our early ramp creatures as well. Also, because its an artifact, we can get it back from the graveyard with Cavalier of Dawn if we happen to mill it with Cavalier of Thorns.

Henge and Kiora do have the major drawback of being legendary however, meaning any copies you draw beyond the first are dead draws, but we have a couple ways to mitigate this. Cavalier of Flame's ETB trigger lets us discard them and redraw, and we also run Vivien's Arkbow, allowing us to discard any card in order to put a Cavalier directly onto the battlefield.

Putting it all together, we end up with a mid-range deck that tries to play a Cavalier per turn, hopefully starting on turn 3, then overwhelms in the late game with one last ridiculous charge.

The Mana Base

We're a four 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 Lotus Field, since that's one of our best ways of finding it. We also need a lot of untapped green sources to enable our early ramp.

We could stick with a nearly mono-green mana base outside of lotus field here, but stretching out into one other color won't be an undue burden on our ability to cast our early ramp creatures, so I've opted to go black for Deathsprout. I know that seems like an odd card to splash a color for, but hear me out: it's exactly what this deck needs. With 8 mana dorks, we will almost always be able to cast it on turn 3, allowing us to slow down aggro decks and guarentee 5 mana the next turn for a cavalier at the same time. And because this deck can always use more mana, and runs 7 basic lands, the ramp upside will always be relevant. It's perfect.

As a final consideration, we want lands in the graveyard for Cavalier of Flame. Lotus Field itself is a good start here, but adding Fabled Passage helps with this while also just being a resonable choice by itself. We do need to run a few extra basic lands to support it, but that helps Deathsprout too, so that works out.

What we end up with is 25 lands (which should give us land drops for the first 4-5 turns), a strong commitment to green, a fair number of black sources, a couple white ones' a single Mountain to make activating Cavalier of Flame easier, and two Castle Loctwain because it can be activated with a single Lotus Field, and it's really good emergency mana sink if we stall out. Keep in mind Cavalier of Thorns can help us find the castle as well, and that between Kiora, Behemoth Beckoner and The Great Henge a single good draw can snowball into many more.

Because Fabled Passage and Deathsprout give us so much choice over what colors we get, we can usually cast Cavalier of Dawn or Cavalier of Night (but not always both) without Lotus Field. We have no hope with Cavalier of Flame of course, but that's our finisher, and by far the worst Cavalier defensively, so that's less of a concern than the others.

Tips & Tricks

Between Cavalier of Thorns, Cavalier of Dawn and even Cavalier of Flame on-death effects, the graveyard is a resource for this deck. Cavalier of Thorns's ETB ability is the most obvious way to fill it up, but Cavalier of Flame's ETB also 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, Deathsprout, and Cavalier of Thorns ETB effect when putting a card on the top of your library with Cavalier of Thorns. 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, planning to sacrifice Thorns. 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, The Great Henge or Cavalier of Flame. In really dire situations, you can order a Night or Dawn trigger before your draw effects to kill off a Thorn and get a card back in your library.
• 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.

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. With Gilded Goose enabling a turn 2 Kiora, this can lead to a turn 3 Cavalier.

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

Be careful playing Cavalier of Thorns of you don't have at least two non-lotus lands. Putting a land onto the battlefield is not optional, so if all you find in the top 5 cards of your deck is a Lotus Field, you will have to play it. This isn't super likely to happen, but it's devastating if it does, so just try to avoid situations where it could happen.

Sideboarding

First, let's just go over each card, and what they're here for.

2 extra Vivien's Arkbow come in against counter heavy decks, or slower more control focused decks in general, since it basically gives you the ability to cast uncounterable Cavaliers at instant speed off the top of your deck in the late game. Typically these will replace ramp creatures in these matchups, and you probably won't want all of them unless your opponent is playing Simic Flash, or a similar pile of nothing but counters.

3 Murderous Rider as strong early removal against aggro. It's not bad against SuperFriends, or creature based Fires of Invention decks either, but you may want to leave a few of these out in slower matchups to make room for restocking options like Kiora, Behemoth Beckoner, The Great Henge, or Vivien's Arkbow. Against aggro though, these are very important. Despite the prevalence of green based aggro, we still run these over Noxious Grasp because we need an early removal card against Mono Red and Embercleave Knights, or those decks will run over us. And once we've dedicated some slots to that, we don't need any more removal specifically against green.

3 Planar Cleansing mostly as a board wipe against aggro, but with the upside of also destroying Embercleave, Lucky Clover, and Witch's Oven, Fires of Invention, and Trail of Crumbs. In all, it's the strongest board wipe in the format, except for its unfortunate inability to kill lands animated by Nissa, Who Shakes the World. We can usually suffer that downside alright though, because our creatures are much bigger than Nissa's leftover lands. Don't be afraid of casting this when you have a cavalier or two on the board, their death effects coupled with our ability to return them later with Knights' Charge will mean that exchange usually works in our favor.

4 Duress to help against control, and especially flash decks.

1 extra Cavalier of Flame against slower matchups, and particularly against decks without creatures to block it.

1 extra Cavalier of Night for aggro matchups where the creature removal and lifegain are especially relevant.

2 Trostoni Discordant Because we live in mortal fear of Mass Manipulation and Agent of Treachery. It's not terrible against aggro  decks either, especially ones that rely on smaller creatures like Cavalcade of Calamity decks, so that's nice.

Against aggro decks, you're going to want to trim your late game options. Consider cutting Vivian's Arkbow and a The Great Henge or two. Cavalier of Flame is worth dropping entirely, and it can sometimes be worth it to drop a single Knights' Charge if you need the space.

Against slower decks you can typically trim Gilded Goose. Their early removal will make it much less likely you get to ramp effectively with it, and you don't need the increased tempo anyway. Paradise Druid is still valuable though, because the hexproof makes it much harder to remove.

If your opponent isn't running creatures, Cavalier of Night becomes much less valuable, and should probably be cut completely.

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 most of the removal we have for it. If you even suspect your opponent has this, bring in all the Murderous Riders post-board, and make sure you keep all the Deathsprouts.

Wicked Wolf is very hard for us to answer. We have no exile effects, and it gets bigger than our cavaliers. Once it's played, we basically have to hope we can chump block it long enough to win with Knights' Charge. But from my testing so far, this hasn't been as hard as I thought it would be. Cavalier of Night in particular gets us four life and two chump blockers against it (since we get a creature back when it dies), so we can typically survive quite a while with it on the board.

As mentioned previously, theft effects like Mass Manipulation and Agent of Treachery are very strong against us. Not only can our opponent get themselves some very strong creatures this way, but they deny us our death triggers and the ability to resurect our Cavaliers with Knights' Charge. The Trostoni Discordants in our sideboard are a reasonable answer to this, but if our opponent has these effects in their main deck, game one is going to be rough.

Oko, Thief of Crowns was the bane of our existence, and I'd just like to take a moment to dance on his grave. Very glad he was banned.

Final Thoughts

The Once Upon a Time ban hit this deck pretty hard, but I think this version bounces back nicely.

And its still really fun to play. Watching ETB triggers stack up after activating Knights' Charge is some of the most fun I've had with magic, and this deck provides that for me very consistently.