To me, the breakout Modern development of 2019 wasn't the long-awaited Stoneforge Mystic unban, the rise and fall of Arclight Phoenix, or the frightening flash of Hogaak, Arisen Necropolis. Rather, it was the introduction of cheap planeswalkers on a massive scale. Beginning with War of the Spark, Wizards unleashed on the format gameplay the likes of which we'd never seen: matches decided by hard-to-answer value machines with relevant static abilities resolving, sticking, and grinding opponents to a halt.
The trend continued with Modern Horizons, whose printing of Wrenn and Six single-handedly revived Jund while enabling a host of lesser decks; now, the cheap-walker tradition extends to Throne of Eldraine, which brings Oko, Thief of Crowns to the fray.
Today, we'll look at how cheap walkers came to define the format.
Pre-Game: Liliana of the Veil
Of course, cheap walkers weren't entirely new to Modern when War rolled around; Liliana of the Veil had spent many years representing for the card type. But it was pretty much just her. These days, despite still ranking as one of the format's better black cards, the walker has quite the competition.
As a standalone card, Liliana interacted with the board at an unprecedented rate, not only offering players a then-unprinted Edict effect but an upticking value machine that promised even more removal down the road, all while heavily disrupting critical-mass and control-slanted decks.
Planeswalkers as a card type reward players boasting enough interaction to resolve and protect them; in other words, midrange decks. Liliana's double-black requirement joined with Thoughtseize's color identity to make black-based midrange the dominant flavor throughout the format's history. Fatal Push proved the nail in the coffin for that battle—while we do occasionally see, say, Temur-colored midrange decks rear their heads, the strategy is overwhelmingly black-dominated, something I don't expect to change any time soon.
With that being said, printing cheap walkers in other colors is a definitive first step to diversifying the color profiles of midrange strategies.
First Wave: War of the Spark
War brought numerous three-mana walkers into Modern, shaking Liliana's standing as one of the format's lynchpins.
Narset, Parter of Veils
Narset, Parter of Veils was an early hit from War thanks to the then-stifling presence of Arclight Phoenix. The walker's static ability shut down not just Phoenix, but other Faithless Looting decks, completely debilitating cantrip-heavy strategies while simply peeving less-reliant shells.
Format effects: gives blue-heavy decks a mainboardable way to hose velocity strategies
Winners: UW Control, blue-based aggro-control
Even against decks without cantrips, though, Narset won her weight as a card, immediately digging for a spell and then doing so again the following turn should she not eat a Bolt. That super-Divination would leave behind the static ability. Even if she was answered in the following turn cycle, Narset ended up plussing, as her removal still cost opponents a card if they didn't have threats ready to swing at her. UW Control, a deck great at keeping the board clear, ended up being Narset's forever home.
Teferi, Time Raveler
Another UW standby, Teferi, Time Raveler offers similar benefits: the walker presents a card advantage engine as it disrupts opponents with a static ability. While great at pushing through threats in control mirrors, Teferi's found more success as a self-replacing piece of soft-disruption in tribal aggro strategies like Spirits, or a wall of insulation against enemy disruption in combo decks such as the ubiquitous Urza.
Format effects: lets combo-based decks happy to splash it employ a proactive floodgate plan against instant-speed disruption, all while staying even on cards
Winners: Urza, Infect, Spirits
Saheeli, Sublime Artificer
Continuing the daisy chain is Saheeli, Sublime Artificer, another player in Urza decks. Saheeli provides a Plan B to anyone casting noncreature spells, be they artifacts or instants and sorceries—indeed, we've seen this walker make a splash in decks as diverse as Mardu Midrange and Arclight Phoenix.
Format effects: forces opponents of blue or red decks with access to Saheeli to remember their sweepers after sideboard
Winners: Mardu, Phoenix, Delver, Urza
Ashiok, Dream Render
Finally, we land on Ashiok, Dream Render, the last of War's walkers to make a lasting impact. Ashiok has by and large been a sideboard card since its printing, but it remains one of the top-played walkers in the format for the many types of hate it provides. Between nuking the graveyard, preventing enemy searches, and potentially removing key cards from the opponent's deck, Ashiok poses a nightmare for plenty of strategies. As it doesn't impact the board, though, it's often too risky to run in the maindeck; nobody wants to be aggro food!
Format effects: Makes search-heavy and grave-synergy decks more cautious against blue and black midrange decks
Winners: Ux and Bx midrange/control strategies
Shakeup: Modern Horizons
Horizons isn't known for its planeswalkers per se, but it did drop into circulation what I'd call the most powerful planeswalker in Modern: Wrenn and Six. At just two mana, Wrenn promises to snowball card advantage for any fetch-heavy deck (read: most of them) if not dealt with posthaste. And rapidly killing a 4-loyalty walker isn't very easy for anyone to do, making Wrenn an ideal follow-up to a deceased mana dork or other play on an empty board.
Format effects: Adds an early-game dimension to games featuring x/1s, incidentally hating on those decks, and provides players with a Dark Confidant-esque card-advantage engine during the early stages
Winners: multicolor midrange decks
That's not to mention Wrenn's -1 ability, which I'd argue has impacted the kinds of creatures Modernites can safely sleeve up. x/1s now need to pass an even higher bar to meet playability standards. Gone are the days of futzing around with synergy-creating 1/1s; Wrenn plays like a super-Liliana when it comes to dealing with those. Here it is in Jund:
Wrenn has also enabled plenty of multi-colored decks, including the 4-Color Snow lists wielding Arcum's Astrolabe. Hitting a land drop each turn, and especially a fetchland, ensures that these decks have the colors they need, and in the right amount.
Belle of the Ball: Throne of Eldraine
Our last stop is Throne of Eldraine, Magic's newest expansion. Throne has already begun to significantly impact Modern, not least of all because of one, maybe-Standard-bannable planeswalker: Oko, Thief of Crowns.
Oko gives the Simic combination something it's never had access to in a solid removal option. While turning fatties into Elks doesn't exactly remove them, it might as well when it comes to abilities. Besides, a 3/3 is much easier to deal with than, say, a 6/6. After just one full turn cycle on the battlefield, Oko can also steal enemy creatures with its ultimate, trading away a nigh-useless Food token for whatever Goyf opponents are hiding behind.
This combination of abilities makes Oko attractive even in low-curve strategies such as Traverse Shadow. We're also seeing it in Bant Company, a deck beginning to enjoy an abundance of attack angles thanks to its other recent addition in Stoneforge Mystic. Heck, even UG Merfolk is making a comeback with Oko in its ranks, and UG Eldrazi don't look too shabby, either.
Format effects: Grants UGx decks a solid, on-color removal plan doubling as a value train
Winners: Anything in those colors
But these uses aren't what's got most of the format's attention right now. That honor goes to Oko's newfound role alongside Urza, Lord High Artificer. With Emry, Lurker of the Loch looping cheap artifacts and Oko turning them into 3/3s, the deck is beginning to resemble Hogaak in its ability to pump out bodies nonstop and resist targeted hate (in this case, Collector Ouphe).
It seems a bit early to tell if Oko Urza will retain its title as the go-to Urza build in the future, but it is a force to be reckoned with currently.
Wizards's apparent willingness to print great, cheap walkers bodes well for Modern's future. Walkers are unique enough in their individual design that most cheap ones with decent abilities should find a home somewhere, keeping the format from getting too stale. But if the company does decide to ban Oko from Standard, perhaps they'll decide (also informed by Teferi's performance) to tone back the power level of these permanents. They are indeed divisive, with Jon Finkel going so far as to claim planeswalkers in general ruined Magic.