Ready thy noble' steed, fair knight. Sound the horns and let the heraldic banners fly. For your chivalric quest has just begun. Readily, thou' will face many a danger along the journey. But with steely heart and tactical prowess, you're surely ready for whatever fate throws at you.

Especially if you can outflank your adversaries.

Knights are big on marketing. Brand logos and all.

Ask a random Magicplayer to name an ability intrinsic to knights, and you're likely to hear First Strike, Double Strike, perhaps Haste, or if they're an old-soul, protection from Black or White (White Knight vs. Black Knight, the classic rivalry). Though Magic's many knights (almost 500!) wield a range of abilities, only one refers to the mounted nature of these warriors atop horseback. Okay fine, aside from Horsemanship (Guan Yu, Sainted Warrior). When plated head-to-toe in steel, mobility is sure to take a hit, so knights frequently employ mounts while charging into battle. These brave beasts not only provide speed, but enough maneuverability to quickly weave around and strike the enemy from the side. When it comes to creatures with Flanking, hooves are often just as involved as helms.

Sometimes they even belong to the same owner:

Background

Debuting in 1996's Mirage, Flanking was the go-to mechanic for various knight factions across the block (Mirage-Visions-Weatherlight). Though primarily centered in White (Femeref Knight, Sidar Jabari, Zhalfirin Commander) and Red (Telim'Tor, Suq'Ata Lancer, Searing Spear Askari) all colors got at least one Flanking creature (Knight of the Mists, Cadaverous Knight, Jorael's Centaur). We even got a colorless source of the ability via Jabari's Banner. Despite Flanking's first appearance in Mirage, the set also featured its only form of punishment in Barbed Foliage. Even when you flash-forward to today, there are only 32 creatures with the ability, including the oddballs like Old Fogey and Flanking Licid, so most Commander players are likely after the Foliage's Caltrops-effect rather than anti-Flanking tech.

Jump ahead a few hundred years to Time Spiral, and Flanking makes a return, although this time with a decidedly-Mad Max wasteland warrior aesthetic. Dominaria is beset by global catastrophes and time rifts, and as such, the set is rife with post-apocalyptic tropes. Fitting, as the last set of the Phyrexian Invasion was literally called Apocalypse. Once again, Boros got the lion-share of the ability (Gustcloak Cavalier, Blazing Blade Askari), though there is the potential for 5-color chaos if Sidewinder Sliver can introduce it to the rest of his Hive.

Like with Mirage, most of Time Spiral block's Flanking creatures were designed for Limited play (Benalish Calvary, Riftmarked Knight, Skulking Knight), so Commander will need a future set to revive the mechanic if a proper 100-card deck is ever to materialize. Sidar Kondo of Jumaraa, Telim'Tor, and Sidar Jabari may wield it, but only Telim'Tor has any real synergy with the ability.

Unless we count Odric's evil twin in Oddric, Lunar Marquis. You know you're in trouble when 10% of your options are memes.

Rules

A purely offensive ability, whenever a creature with Flanking attacks, any creature blocking it that doesn't also have Flanking gets -1/-1 until the end of turn. The -1/-1 is dealt out once a blocker is declared, before damage is exchanged. However, even if the shrink-effect kills the blocking creature - say it's a mere 1/1 token - the attacker is still considered blocked. And such, its damage won't go through to hit your opponent. Most of the time, at least. Like with all things in Magic, even the most straight-forward of abilities come with hidden nuance.

Add Trample to the mix, and things get interesting. Much like how Ride Down kills the blocker first, allowing Trample to deliver an attacker's assault onto opponents even after blocks, Flanking also helps push through damage. If your attacking 3/3 Pentarch Paladin is blocked by an enemy 2/2 Zombie token, the zombie would reduce to a 1/1 due to the paladin's Flanking, but the attacker would still be considered blocked. However, let's say you cast Charge Through on your Paladin after blocks were declared. Now excess damage carries over due to Trample, and because Flanking reduces the power/toughness of the blocker, more punch gets through. In this scenario, the Pentarch Paladin would kill the blocking zombie and send two damage to your opponent, as Flanking made the Zombie a 1/1 until the end of turn.

Flanking also stacks, meaning additional instances of the ability on an attacker will result in a greater degree of -X/-X for blockers. Take the above example, but now assume you also have Calvary Master in play. Now your Pentarch Paladin has two instances of Flanking, giving the zombie -2/-2 upon blocks, killing it before damage is dealt. Cast Charge Through on your paladin before blocks, and his full three damage would hop straight to the opponent, blockers be damned. Knight of Valor has a built-in version of multi-Flanking and will function in much the same way. This stacking-effect makes Jabari's Banner useful even in decks already full of Flanking creatures.

Timing also needs to be taken into consideration if a creature with Flanking is attacking you, as the status-effect will take place upon declaration of blockers. If you want to cast your own pump spell on a creature to save it from smiting, be sure to do so before you've declared it as a blocker. If you block with your 1/1 Squirrel, cast that Giant Growth on it the moment an attacker turns sideways, or Flanking will axe the poor little critter before your pump spell can save it.

While it's been a while since we've last seen Flanking, I'm hopeful future sets will bring the ability back for more. Now that Zhalfir has phased back into the Multiverse at the end of March of the Machine - Teferi had initially phased it out to save it from the original Phyrexian invasion, illustrated on Teferi's Protection - there's a perfect thematic segue. As you can see from newer cards (Invasion of New Phyrexia, Sidar Jabari of Zhalfir, Marshal of Zhalfir), Zhalfir already has a strong Knight-theme, and Flanking fits in perfectly, especially when you consider some of the originals like Zhalfirin Knight. Here's hoping these noble knights will see their signature mechanic make a triumphant return, and with it, a viable Commander deck.

Thanks for reading, and may you forever outflank your adversaries!

-Matt-

@Intrepid_tautog