The tap ability of Relic can make me play differently. Against a slow-ish Blue deck I will simply draw and discard dredgers instead of casting spells. The relic stops that line of play completely.

@Ben
I hadn't even considered this for Dredge, but you're right of course. It is also helpful against ANT because it protects my draw spells from Duress. The SB data you've presented match what I have experienced.

Legacy Dredge isn't able to mulligan super aggressively, the way Vintage Dredge can, because they still need to put together an enabler, a dredge card, and mana to cast the enabler. If Dredge is willing to SB 4 Leylines you have a 40% chance of seeing it in your opening 7, a 61% chance of seeing it in your 7 or your 6, and a 73% chance of seeing it in your 7, 6, or 5. Are you willing to mulligan to 5 to get to your anti-hate cards? What if you mulligan into a Leyline but no enablers or no dredge cards? Are you keeping then? And, of course, any Leylines you draw subsequently will be dead cards.

Additionally, your opponent may end up playing different hate cards than you expect. Relic of Progenitus works just fine under Leyline of Sanctity – the tap ability was already irrelevant in this matchup because Dredge always had the ability to get chaff into its graveyard. Faerie Macabre has been on the upswing as an anti-graveyard SB card. And of course there is still Leyline of the Void. The nightmare for the Dredge player is when your opponent brings in a bunch of different hate cards – what do you do if your opponent brings in a Crypt, a Leyline, a Relic, a Trap, and two Macabres? Are you willing to mulligan aggresively to a Leyline of Salvation if it only shuts down a third of the hate cards? Do you bring in 4 Leylines AND pithing needles AND bounce?

Leyline of Salvation may be good against unprepared Legacy players that simply add 3 Crypts to the SB and call it a day, but against the savy players it's not going to be an effective anti-hate option, and those are the players you wanted to shore up your matchups against in the first place …

Ravenous Trap
Tormod's Crypt
Bojuka Bog
Relic of Progenitus

A quick check of deckcheck.org shows the following as the most popular anti-dredge sideboard cards in Legacy over the past 3 months: Relic of Progenitus, Tormod's Crypt, Ravenous Trap. All three of which are stopped by Leyline of Sanctity.

So basically, Dredge decks (which were held in check by easy-to-cast Graveyard hate: A zero mana artifact, a one-mana artifact, a land, and a 0-cost spell that pretty much can be cast at any time) will have a ridiculous sideboard option, making Leyline of the Void pretty much the only viable turn 0-1 option to shut down dredge post-board. Moreover, Dredge can aggressively mulligan to their Leyline – good luck to other decks who want to go down to 4/5 cards looking for Leyline of the Void game 2.

– Ben

Is Sphere of Law a better sideboard card for Stax against Burn than Warmth would be? Seems like a very similar effect for 2 mana less. Sphere seems better against Keldon Marauders, Sulphuric Vortex, and Goblin Guides, but otherwise they seem comparable. Maybe the dealing with Vortex by itself is worth paying 2 more mana …

Your rationale certainly makes a lot of sense, and it sounds like a good solution for your particular connundrum.

I appreciate the thoughtful discussion. Keep it up!

Check out the latest TMI from Starcistygames. All of the top decks with Wild Nacatl had 3-4 Mindbreak Traps sideboard!

So it becomes a question whether Leyline is better than Mindbreak Trap. I'm not certain that it is, but the fact Zoo can play it turn 0 to dodge discard from ANT seems pretty good to me.

There's no real presence of mono-black or mono-red in my metagame, so I honestly didn't even consider those options. It seems like a reasonable thing to at least consider in both of those cases, although I'm unsure whether there are better sideboard cards or not. But these aren't widely played decks, so unless you have a particularly skewed local metagame they don't seem worth wrrying about.

It still doesn't seem impactful though in "normal" Legacy metagames – it just doesn't hose any of the mainstream decks sufficiently to seem justified as a sideboard card, and as Robert points out the one deck that it might make sense to run miandeck (Enchantress) already has a superior card (for their purposes).

I want it against the mono red matchup and the mono black matchup. Hymn to Tourach wrecks me all day long.

I mean you could be right but it's worth exploring the implications. Unless you are instantly right with every snap judgement you make. 🙂

Clearly you don't want it against Merfolk, Goblins, Lands, New Horizons, NO Bant, or CounterTop Thopter, as they have no spells that target opponents that matter in the matchup.

You could play it against Zoo to prevent them from burning you out, but there are better sideboard cards that you would prefer to have first.

It would be fine against Reanimator and Storm combo, but you should already beat Storm Combo, and Reanimator hasn't proven itself to be a deck post MT banning. And even in these cases it seems like it is merely "fine" and not great.

Am I missing something?

If the card would get played, it would only be a metagame response to Oath of Druids in Vintage. As such, trade for foils if you can get a good deal, but this card strikes me as very bad for Type 2 play. Four mana is the critical turn of type 2, and this is an extremely underwhelming play at that turn.