One, Two, Three Times the Murder: Sideboarding Strategies and Tactics, Part 2
...which would you predict was the more successful sorcery?
Tidings was a reasonably played sorcery in the Standard of its day and age, primarily in the mana-crushing UR Magnivore deck... but it wasn't Thoughtcast. Thoughtcast was the glue that peanut buttered together the greatest offensive deck in the history of Magic: The Gathering.
The simple answer is that Thoughtcast didn't actually cost five, at least not for practical purposes. Sure, it had 
in the upper-right corner, but Thoughtcast acted much more like a Sleight of Hand that let you keep both cards for than the Tidings that might invite a direct casting-cost comparison. Put another way, you could often play all four Thoughtcasts in an Affinity deck before you paid the full five of a Tidings!
Here is something that might have never been made explicit for you:
More games are determined by a player's ability to get cards online (first) than any other factor. That's what makes fast mana so dangerous (you can get lots and lots of cards online, even if it costs you cards). That's why we complain about manascrew (couldn't get cards online) on the one end... but also why cheaper cards are more effective than more expensive cards. You know, like Lightning Bolt (a one-mana instant) being maybe the best red card in history versus Volcanic Hammer (a two-mana sorcery) being a fringe playable only in certain decks.
Now a comparison between Lightning Bolt and Volcanic Hammer might be intuitively obvious, but what about these two?
Murder from last year's core set... kind of never caught on. Even though we finally had our nigh-unconditional "kill anything" and players generally preferred any and every two-mana analogue ever to it. Doom Blade and Go for the Throat went eight-pack in Standard when they could. Even Victim of Night was generally more popular despite the prevalence of threats like Stromkirk Noble and Geralf's Messenger.
But what about Deathmark?
You can't easily imagine a less-versatile opposite number to Murder. Where Murder hits almost everything, Deathmark misses like 40% of the time. Where Murder is an immediate instant, Deathmark is a slow sorcery.
And yet? Deathmark saw play in a wide variety of decks in a wide swath of formats... Affinity decks, Psychatog decks, any decks that wanted to kill a green or white creature efficiently.
What is Deathmark's secret? If you can just make sure your opponent is playing green and/or white, you guarantee that you have a super-efficient response card: It just doesn't get much better and faster than "one mana, kill anything." You probably already know how you can control for colors: Deathmark was primarily a sideboard card.
When we left things in "Sideboarding Strategies and Tactics, Part 1," we were just about to hit on color-specific sideboarding. Which is kind of backwards, as color-specific sideboarding is one of the most straightforward and basic types of sideboarding strategies. It should be obvious why:
At the same total casting cost, one of them blows up all the lands (including mine); one only blows up your lands... and at instant speed! Classic R&D making it easy.
Color-specific sideboard cards come in many shapes and sizes. Some are bombs like the aforementioned Boil... hit it and the opponent is in a world of trouble... like a Mind's Desire with a guidance system. Some are unbelievably fast and flexible, like Pyroblast or Blue Elemental Blast: they do almost anything you could want in a matchup, from stopping a key spell (you know, like a Boil—and cost-efficiently!) or destroying a dangerous permanent even after it has resolved. Some cards, like Circle of Protection: Red, Karma, or Gloom are themselves powerful permanents. Neither red nor black has ever been particularly good at removing enchantments (and neither had an easy road to winning while one of those was on the battlefield). Gloom was easily destroyed by white's Disenchant... only Disenchant cost a painful five mana against Gloom: quite the opposite of desired sideboard efficiency.
Some color-specific sideboard cards just help you get your cards online faster than the opponent.
Gainsay | Art by Clint Cearley
Before it was the Magic Online handle of one of the world's finest deck designers, Gainsay was the quintessential blue-against-blue self-hating hoser. And in Theros, Gainsay is back!
Gainsay is more than meets the eye. You can use it as an efficiency swap, removing a three-mana Counterspell a la Cancel and making yourself a wee bit faster with a two. Blue decks have been doing this in Standard for some time with spells like Negate and Dispel, both of which make blue decks faster and more interactively relevant against one another. Negate can stop Jace, Memory Adept and Dispel trades one mana for X against Sphinx's Revelation. Awesome and awesomer!
...now stack either or up against Gainsay. Negate doesn't stop an Ætherling. Dispel can't hold off Ral Zarek. But as long as you can aim (at blue), you—rather blue—can't do much better than a Gainsay.
Dark Betrayal | Art by Nils Hamm
Continuing the theme of self-hatred and speed, Dark Betrayal is the next step in Deathmark and Human Frailty: a highly focused creature-kill card for only one mana.
You can use a card like Gainsay to get more efficient than your three-mana counterspell, or overload the opponent in a sea of permission... but what about Dark Betrayal? The default main-deck black point-removal spell is a card like Doom Blade. "Just dies to Doom Blade," is the kind of thing you hear all the time... only that clearly isn't the case all the time. Neither a Bogbrew Witch nor a Xathrid Necromancer is lining up to "just" die to Doom Blade. When facing another black deck, black decks will very often have dead weight in the form of a card like Doom Blade.
Dark Betrayal is a perfect example of a swap that does two things well, and simultaneously. Not only does it lower your casting costs, making your deck faster (ergo, able to get cards online even faster)... but when you are replacing a default like Doom Blade you can actually be removing a liability while adding an asset. That's almost like three good things!
Hunt the Hunter | Art by Ryan Barger
Hunt the Hunter is probably my favorite card of this cycle. While it's not fast—as in it's not an instant (and the development team probably had good reason for that)—it's cheap. And it's not just cheap, but it does a ton of stuff for that one 
.
Hunt the Hunter is first and foremost a pump spell. While not exactly a two-for-one (at least not unless you are taking out a creature that is wearing an Aura), Hunt the Hunter makes a potential attacker big. So you can knock a wannabe blocker out of the way and get in for a little bit extra. Two-thirds of a Giant Growth ain't nothin' to shake a stick at, especially when it is taking a creature down on the way to punching the opponent in the face.
Hunt the Hunter is a green removal spell (more-or-less). One of the creative limitations on green is that it doesn't normally get cards like Lightning Bolt or Doom Blade. All its removal is based on battle. Cards like Simian Grunts or Beast Attack could be "card advantage" removal spells, taking down attackers and leaving a potential counter-attacker. The problems with those kinds of cards are that they are not just expensive but telegraphed. So... you are leaving up five mana with a full grip? Um... no attack? Hunt the Hunter hasn't got either limitation, but neither is it unconditional like its black or white cycle brethren. You need a creature. You need it to be green. Lots of stuff can go wrong. But when it doesn't? You are probably in for a substantial swing on the battlefield.
Hunt the Hunter is quintessentially green. I love the implementation here, not just from a game-play standpoint (this is obviously going to be awesome at breaking up creature standoffs) but the flavor. Of course this is how you implement green-on-green violence. Fight!
Glare of Heresy | Art by Raymond Swanland
It should be pretty obvious by this point that we are talking about a cycle of Theros sideboard cards that specialize in fighting their own colors.
Of these, Gainsay is almost perfect; Dark Betrayal is like an echo of another cycle (not just this one) killing green and white stuff, killing Humans, now killing black creatures; and Hunt the Hunter is not just a cool playable but a triumph of flavor. Glare of Heresy is like Dark Betrayal glued to Hunt the Hunter. White does have a history of great exile effects like Swords to Plowshares, Path to Exile, or Revoke Existence... and Glare of Heresy continues that theme and multiplies it across many different contexts.
White has both great fast creatures and great powerhouse creatures. Glare of Heresy kills both kinds of creatures, slowing down rush cards and cutting off haymakers. For white control decks, it is also one more fast elimination card knocking down the defense of often hard-to-hit Fiendslayer Paladin (who so often is covered in cards).
Exiling a Detention Sphere is particularly exciting because you get cool stuff back. Other enchantments like Angelic Accord and Unflinching Courage are game-breakers that are equally eligible for exile.
Planeswalkers. Check. "Permanent."
"Indestructible." Heh. Although you have to wink and smile at Glare of Heresy taking down the white god.
Like the other cards we've looked at, Glare of Heresy is quite obviously going to have some serious impact in Standard and probably other formats so long as white produces permanents of any type. It only costs two mana—meaning it gives you fast defensive deck speed—and can also trade quite a leap up against the opponent's mana investment. It might just work nicely with Snapcaster Mage... while knocking out troublesome permanents like Gaddock Teeg or Thalia, Guardian of Thraben in Legacy. Of all the many quite-good cards covered in this cycle, Glare of Heresy comes the closest to being everything to everyone.
Peak Eruption | Art by Adam Paquette
The maybe-oddball of this cycle is Peak Eruption. All the rest of the cards counter, destroy, fight, or exile a spell, creature, or other permanent of a particular color. On the other hand, the word "red" doesn't even appear on this card! Peak Eruption doesn't do any of that; it is basically a thematically realigned Cryoclasm.
Will Peak Eruption hate on its own strategy? Often, I'd bet. Sometimes. But it will have a different kind of agenda as well. The card is costed like Stone Rain, a card that is now considered too powerful—or at least too fast—for Standard play. But it isn't just a Stone Rain—it packs Lightning Bolt to the jaw at the same time. As one way we measure the efficacy of red spells is how much damage they do, Peak Eruption can be kind of like card advantage. You can think of a card like Hunt the Hunter breaking a mirror-esque standoff, or how a Gainsay fight might come up during one player or another's end step; but Peak Eruption? It might as well be Cryoclasm!
I can totally imagine a Peak Eruption as a follow-up to a Young Pyromancer on turn three; or a Big Red setup spell... against the Steam Vents or Sacred Foundry in RWU Control.
Peak Eruption is an interesting note to finish discussion of this cycle because—even aside from the fact that it hits lands and not particularly colored cards—it doesn't really fall under the category of color-specific sideboarding. It will be rare that this card can make a deck faster (although, to be fair, it can certainly make the opponent come out more slowly), it isn't really a threat to win (except when paired with eight or so more direct-damage cards), and it isn't going to dig you out of danger when the opponent comes out quickly (unless the opponent has already taken 17).
Unlike the other four, it's not an answer.
Peak Eruption is a potential monster against midrange and control decks like Jund or Grixis, putting pressure on the opponent—even painting him or her into a corner—but I don't know that it would be particularly desirable in a fast red or even Big Red mirror, especially on the draw. The games where the opponent lays out a Rakdos Cackler, a Lightning Mauler, and Boros Reckoner are unlikely to be resolved by a Stone Rain + 3 damage. Which is not to say Peak Eruption isn't a solid card... because when you've already got the initiative, this is a solid sorcery for keeping it, as it will keep the opponent from getting cards out quickly.
All five of these new (well, four new and one returning) Theros cards are going to see competitive play. They do many of the things that good sideboard cards do. They make decks faster, make them more precise, and help them win contests on the battlefield. Well, four of them, anyway.