This month, Ravnica: City of Guilds turned twenty. Released in October 2005, after the tumultuous years of Mirrodin and Kamigawa blocks, Ravnica came at a time when Magic needed an unqualified win to draw back in lapsed players and course-correct stagnant tournament play. The fact that we're still playing two decades later ought to tell you whether it succeeded, but I'll just underline it: Ravnica saved Magic. Ravnica Limited was fantastic, the color fixing and multicolored cards made Standard a brewer's playground, and the Guilds were one of Wizards of the Coast's most brilliant marketing strategies, tying gameplay mechanics and philosophies to player identity. Aside from Dredge, which became a multiformat boogeyman that shaped tournament play for a decade (and even then, I would argue Dredge was a positive development for the game's legacy), there's little to quibble about Ravnica: City of Guilds.

That's not to say the block is perfect - many of the cards, which set benchmarks at the time, have been made obsolete by later evolutions, and some of the guild mechanics were more successful than others. For every Convoke or Bloodthirst, there's a Forecast or a Haunt. But perhaps the most forgotten mechanic - seriously, quiz your nearest Magic old head on the 10 Ravnican original guild mechanics - is Boros's Radiance.

Radiance was an ability word representing the troop-boosting battlemagic of the martial guild. Any effect with Radiance will radiate outward to each creature that shares a color with the initial target. The real issue with Radiance is that it's symmetrical. So, if you target a Rakdos Guildmage with a Cleansing Beam, it will deal two damage to the Guildmage, any Dark Confidants or Goblin Guides on the field, and - somewhat problematically - your own army of Skyknight Legionnaires and Boros Swiftblades. (Note also that, should the target become illegal, say with Fiery Conclusion, the original Radiance spell will fizzle entirely.)

Radiance was suboptimal in both gameplay - it was unpredictable based on what your opponent was playing, so your Brightflame could end up more of a universal boardwipe than the Plague Wind it purported to be - and in flavor. Conceptually, I like the idea of a guild so monomaniacally focused on battle magic that friendly fire casualties are seen as acceptable sacrifices, but it doesn't feel , more Mardu. There were incredible innovations in Ravnica: City of Guilds, but Radiance was not one of them.

I say "was" because Radiance only ever showed up in that single set. Per Mark Rosewater, "Radiance is not a beloved mechanic. I believe it is the least liked of all the guild mechanics. It's also hard to design cards for." It ranks at 9 on his Storm Scale, meaning it is extremely unlikely to return, although even mechanics that high are fair game for cameo mechanics or one-offs in Commander decks or Modern Horizons sets. Radiance does have fun synergy with cards like Transguild Courier or Fallaji Wayfarer (and serious dyssynergy with Devoid and other colorless cards), so I wouldn't expect it to ride the pine forever, but isn't likely to look just like the original version. The Radiance cards we have right now are likely to remain the only ones we get for the foreseeable future.

Of the Ravnica Radiance cards, the best is Rally the Righteous, your classic "win out of nowhere" in conjunction with a bunch of tokens Limited staple. It essentially self-counteracts the drawback of Radiance, as you may untap and boost a handful of your opponent's creatures that are either Red or White, but if you're casting Rally, you're probably happy with a messy combat. It also functions reasonably well as defense. It was a high pick in Ravnica Limited, where it could intersect with aggressive Boros, Gruul, or Rakdos decks. It sees little play in Constructed formats and very little in Commander, although Feather the Redeemed and The Jolly Balloon Man can exploit it better than most decks.

Aside from Rally, Brightflame was a one-time Commander stalwart in the format's early days, but it's an often-frustrating card - incredibly expensive to kill anything but the smallest creatures, and unpredictably effective at dealing with your opponents' boards without hamstringing your own. It's still a nice tactical nuke for tokens, but since Boros often tends to be the one making tokens, it's a bit of a paradoxical card. Still, Piru the Volatile, Firesong and Sunspeaker, and Feather the Redeemed are happy to run it.

The failure of Radiance is best displayed through the two most frustrating Radiance cards, Wojek Apothecary and Wojek Embermage, both of which made combat a grueling experience in Ravnica Limited, sometimes for both players. Instant speed damage prevention effect led to board stalls - and often reward the more experienced or bluff-comfortable player - and I saw Embermage turn the end-of-combat step into a math-based bloodbath, which is one of the worst kinds of bloodbaths. Bathe in Light also was a powerful protection spell, but if cast optimally, after blockers or in response to removal, it led to both players pausing to calculate how the rest of the turn would play out. There's a place for that in Magic - I enjoy when matches play out like chess - but it does slow down Limited and lead to frustration for newer players.

Radiance has what I call the Dead Ringer Effect, after Apocalypse's Dead Ringers, where the wording is convoluted enough and the effect unpredictable enough that it's simply not worth the mental strain. With Radiance it's hard to parse what will happen in a given situation, especially when the format has rare but crucial color-changing effects, and it plays even more poorly than it reads. I would argue - and Mark Rosewater and innumerable Magic players would agree - that Radiance is a failed mechanic. That doesn't mean it's gone forever, though.

Chroma, from Eventide, was likewise a failed mechanic, before being tweaked into Devotion with Theros Block. It's possible that Radiance could, in a future color-focused set, be similarly tweaked. It's locked to Red and/or White cards thus far, but it has a role right as Dandan/Forgetful Fish is poised to spike in popularity with the release of a Secret Lair and an attendant surge of awareness in the fan format, which often revolves around color-changing effects and clever plays to swing the game.

In past years, I've been more down on failed mechanics returning, but with the sheer number of cards Wizards is pumping out recently, and the innovation of Modern Horizons sets, unique Secret Lairs, and Universes Beyond sets, I could easily see a streamlined Radiance returning. Until then, I'll have fond memories of a Rally the Righteous on a Boros Swiftblade and attacking for an absurd amount of damage after an opponent took what they assumed was a fair trade, and that's what Magic is all about.