Even though a large portion of Modern Horizons 3 appears to have been leaked by unofficial sources, there are still some powerful cards that have gone completely unseen until this moment.
As we already know with past spoilers, there are a ton of Modern Horizons 3 cards that reference back to powerful cards from Magic’s past.
Chthonian Nightmare

Pay X {E}, Sacrifice a creature, Return this enchantment to its owner's hand: Return target creature card with mana value X from your graveyard to the battlefield. Activate only as a sorcery.
is an obvious reference to the Reserved List card
Recurring Nightmare


When this creature enters, exchange control of this creature and target creature an opponent controls. If you do, you get {E}{E}{E}{E}, then sacrifice that creature unless you pay an amount of {E} equal to its mana value.
is another obvious reference to
Gilded Drake

When this creature enters, exchange control of this creature and up to one target creature an opponent controls. If you don't or can't make an exchange, sacrifice this creature. This ability still resolves if its target becomes illegal.
, a cEDH all-star.
Another cEDH-playable card, that may also see play in constructed formats has just been spoiled, and it is yet another obvious callback. Unlike the previous two examples, however, this card isn’t necessarily weaker than the original card. Instead, it is just different, which is by no means a bad thing.
Strix Serenade

Strix Serenade has a lot of parallels with
Swan Song

The downside to Swan’s Song, aside from it not being able to counter everything, is that your opponent gets a 2/2 Bird for their troubles. In a format like cEDH, this is easily worth the exchange since life is abundant and spells become incredibly powerful very quickly. Swan Song even sees some occasional constructed play alongside decks that specifically want your opponents to have creatures. The
Metamorphic Alteration

As this Aura enters, choose a creature.
Enchanted creature is a copy of the chosen creature.
deck that abuses
Archfiend of the Dross

This creature enters with four oil counters on it.
At the beginning of your upkeep, remove an oil counter from this creature. Then if it has no oil counters on it, you lose the game.
Whenever a creature an opponent controls dies, its controller loses 2 life.
is a great example.
Strix Serenade is a new twist on Swan Song. For better or worse, both these cards are incredibly similar to one another. The only thing that’s different is the types of spells that this card counters. While Swan Song covers enchantments, instants, and sorcery spells, Strix Serenade counters creatures, Planeswalkers, and artifacts. Basically, between these two cards, you cover all of the major counterable spell types in Magic.
Like Swan Song, Strix Serenade costs one mana and offers the countered owner of the card a Bird for their troubles. This should see ample play in EDH and cEDH, and could easily see play in Modern depending on how the metagame develops. That said, a 2/2 flying Bird token is much more dangerous in two-player constructed formats than Commander.
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Emperor of Bones

Emperor of Bones offers an interesting reanimation ability. This card can easily turn a fallen Atraxa, Grand Unifier into a nasty threat for just a few mana. All you need to do is exile it with the Emperor’s triggered ability and get a +1/+1 counter on the Emperor to bring it back. The card does come with an Adapt option, but there are quicker ways to trigger it.
This could add an interesting piece of redundancy to the Collector’s Cage decks floating around the Modern format at the moment. Right now, that deck utilizes Emrakul, the Aeons Torn as the threat of choice, which will not work well with Emperor of Bones. That said, you could easily swap to one of the new Eldrazi Titans or to a threat that doesn’t cause a graveyard shuffle, like Emrakul, the World Anew. In the same vein, this card could act as a second
Goryo’s Vengeance

Splice onto Arcane {2}{B} (As you cast an Arcane spell, you may reveal this card from your hand and pay its splice cost. If you do, add this card's effects to that spell.)
effect in that archetype. All in all, Emperor of Bones has some interesting applications.
The Necrobloom

Dredge has been one of the most broken mechanics in Magic’s history. From
Golgari Grave Troll

{1}, Remove a +1/+1 counter from this creature: Regenerate this creature.
Dredge 6 (If you would draw a card, you may mill six cards instead. If you do, return this card from your graveyard to your hand.)
to
Hogaak, Arisen Necropolis

Convoke, delve (Each creature you tap while casting this spell pays for {1} or one mana of that creature's color. Each card you exile from your graveyard pays for {1}.)
You may cast this card from your graveyard.
Trample
, Dredge has caused problems again and again in various formats. The mechanic is so powerful that it continues to exist in Vintage thanks to
Bazaar of Baghdad

The Necrobloom reintroduces Vintage into the world of Modern once again, but it doesn’t seem egregious at first glance. Granting all of your Lands Dredge 2, there are stronger Dredge alternatives that are still legal within the format.
Where things get a bit more interesting is with The Necrobloom’s other abilities. The Necrobloom provides a 0/1 Plant on landfall but, like
Field of the Dead

{T}: Add {C}.
Whenever this land or another land you control enters, if you control seven or more lands with different names, create a 2/2 black Zombie creature token.
, will start producing 2/2 Zombies if you meet the requirements of having seven lands with different names.
Granting your lands Dredge 2 ensures you can always get what you need back in order to maximize The Necrobloom itself. Otherwise, recurring lands like
Wasteland

{T}, Sacrifice this land: Destroy target nonbasic land.
in Legacy can be disgustingly powerful. Sadly, four mana is a lot of mana for that format.
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Absurd Format Shifts

There are some absolutely incredible cards becoming Modern legal for the first time. Sure, you have a few Commanders coming to Modern like Kaalia, the Vast that may not move the needle much, but some of these lands are much more powerful than they seem.
Cephalid Coliseum, in particular, is a scary reprint for Dredge. You can suddenly fill your grave with Dredge effects and draw cards without fear of your ability getting countered by things like
Counterspell

Barbarian Ring

Threshold — {R}, {T}, Sacrifice this land: It deals 2 damage to any target. Activate only if there are seven or more cards in your graveyard.
could be an interesting upgrade for aggressive decks. Burn could trigger Threshold in the late game, turning the Ring into a better alternative to a land like Ramunap Ruins.
This is far from the only reprints that are new to Modern. Ruby Storm could be a real deck in the format now thanks to Ruby Medallion coming to the format. Whether you’re excited to try out some new cards from Modern Horizons 3, or some old cards coming to Modern for the first time, this is going to be a crazy set.
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