This deck takes parts of Sylvan Plug, NO RUG, MUD, and Show and Tell, shoves them in a mono-green deck and it somehow ends up being playable.
Ancient Tomb, City of Traitors, Green Sun's Zenith, and Elvish Spirit Guide provide the necessary acceleration. The first step is to drop some lock piece like Chalice of the Void, Trinisphere, or Choke while you set up. Sylvan Library is the best filtering and card-drawing engine a mono-green deck has, especially since you don't want any one-drops that will just run into your own Chalice of the Void.
Once your opponent is locked under your disruption you need a way to kill quickly, so you have Natural Order, Ugin, Eureka, or Green Suns's Zenith to do the trick. Eureka may seem odd in a deck that is trying to stop its opponent from their casting spells, but when you put an Ugin onto the battlefield off a Eureka, you won't care too much about pretty much anything they do.
Overall, this deck is incredibly powerful although it's difficult to balance power with consistency. Sylvan Library goes a long way, but other than that you're mostly reliant on the top of your deck. If you want to play a card like Ugin in Legacy, there are obviously some sacrifices to make.