Control decks have always been a tough sell in Legacy outside of the incredibly powerful Miracles archetype because there are so many angles of attack you have to prepare for. Being able to defend against fast combo, aggressive creatures, and prison strategies all at once is often too much to ask for a single deck unless it possesses an incredibly versatile way to answer opposing cards, as Miracles has in the Sensei's Divining Top/Counterbalance soft lock.
The other time we have seen control decks emerge is when they had access to incredibly powerful card advantage spells, most notably Dig Through Time, when Grixis Control, looking much like this list, was popular. Like Grixis Control, this deck looks very similar to the now ubiquitous Delver decks, but without its namesake card.
Years of success has caused the format to warp around Delver of Secrets, and no one will go to a tournament without a plan for dealing with a 3/2 flier on turn one. The entrance of Eldrazi into the format also means cards like Thorn of Amethyst and Chalice of the Void, which punish players who overload their decks with cheap spells, are on the rise. In this context, cutting the powerful creature and going a little bigger makes a lot of sense.
Two copies of Impulse and a single Sensei's Divining Top complement the typical package of Brainstorm and Ponder, and both would be too slow in a tempo deck but offer better selection to make this slower deck work. Snapcaster Mage, Young Pyromancer, and Grim Lavamancer combine to provide some card advantage in the absence of a good draw spell, and True-Name Nemesis is a powerful threat that can certainly invalidate entire swaths of opposing decks and take over a game.
Unsurprisingly, the mana denial elements of a typical Delver deck, Wasteland and Stifle, have been cut in favor of a more robust mana base. This deck will not gain nearly as much value from the small tempo gain since it cannot pressure the opponent as well. However, I am surprised to see zero copies of Blood Moon in this deck, since the wealth of basics the deck plays means the Moon can provide plenty of free wins in much the same way that Stifle and Wasteland do for Delver of Secrets strategies.
Blood Moon would also be excellent against Lands, which I would assume this deck struggles mightily with. It has very few ways to interact with the Life From the Loam engine or a Marit Lage token and does not have the clock to win a race consistently, especially if The Tabernacle at Pendrell Vale contains Young Pyromancer. I would at least have 2-3 copies of Blood Moon in the sideboard, and would consider playing them in the maindeck, perhaps over Vendilion Clique.
The sideboard looks fairly typical, although three copies of Envelop seems excessive to me unless you are expecting a lot of Show and Tell decks. I would say the same about Smash to Smithereens, but with the rise of Eldrazi they are probably necessary to deal with the disruptive artifacts. A copy or two of Jace, the Mind Sculptor against Miracles and other control decks would be a welcome addition, but otherwise this is a well-constructed list.
So if you are sick of having your Delvers die to Lightning Bolt or not quite being able to finish your opponent off before they stabilize, try this deck out. You may even fool some of your opponents into thinking you are a Delver deck, causing them to sideboard poorly and mis-assess their role.