A few quick thoughts on Mnemonic Wall.
The other day, I compared Mnemonic Wall to Eternal Witness. While this comparison still applies, I can’t help but think that the Wall may be even better than I originally thought.
Consider the applications of being able to clear the board with Day of Judgment against an aggro deck, then follow it up with Mnemonic Wall to simultaneously retrieve the Wrath from the graveyard AND put your opponent in a situation where they have to either a) play a creature that the Wall can’t profitably block, or b) overcommit to the Day of Judgment that’s now back in your hand.
On its own, it’s a two-for-one; but in the context of a deck with multiple X-for-one Sorceries and Instants, the Wall can bring back anything from Mind Spring to Mind Shatter, from Day of Judgment to Martial Coup. Or perhaps, “Hm, I think I’ll have that Blightning back, thanks.”
And lest we forget: It blocks! It blocks Bloodbraid Elves and Sprouting Thrinaxes, Kor Firewalkers and Nissa’s Chosen. It’s a great chump blocker to give you one more turn to replay that Wrath. It’s also one more permanent to sacrifice to any Annihilator Eldrazi that may somehow make their way onto the board (not that that’s a great reason to use it, but in a control deck that tends to have few nonland permanents, it’s something to keep in mind at least. Sometimes a land may be more important to keep around than an 0/4 wall).
Lastly, a blurb from Evan Erwin’s Twitter: “Mnemonic Wall seems pretty good with Reveillark in Extended. Just sayin.”
Of course, I’m not sure what else Rise of the Eldrazi has in store for us, but at the moment, Mnemonic Wall looks like an exciting, constructed-playable card that should at least make the short list when building any blue-based control deck.
CURRENTLY READING: The Glass of Time by Michael Cox.
Affinity For Islands 
100% agree. I especially like the wrath/wall soft lock. Seems to protect a certain $60 planeswalker quite well also.
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That $60.00 planeswalker can also bounce back the wall should another instant or sorcery need to be relearned from the graveyard.
I like your argument about how this is better than Eternal Witness in the aspect that the wall forces people to overextend to deal damage. I’ll also add that the wall is blue, meaning that green doesn’t have to be splashed in for recursion.
This card looks like it’ll be fun with Grim Discovery. Get this back + a land, play this and get back Discovery. It’s not Life from the Loam, but it’s going to be in Standard.
Great point about how well it works with Grim Discovery; I didn’t even think of that. I’ve always liked the idea of using Grim Discovery with Gargoyle Castle. Maybe it’s time to start considering some sort of UB deck to grind out card advantage. Sphinx of Lost Truths wouldn’t be a bad fit either alongside Wally Mnemonic and Grim Discovery…
The blue answer to cascade?
Polymorph into Mnemonic Wall into Martial Coup?