One deck to emerge from Legacy several years ago was a Cloudpost-centric deck that gave decks like Miracles fits. Expensive spells made Counterbalance look silly, and uncounterable threats are almost impossible for a control deck with a slow clock to deal with.
The 12-Post decks don’t necessarily even need to have 12 Posts, but the idea is that you can generate mana similar to a Tron deck thanks to Cloudpost. A pair of Cloudposts will allow each to generate 2 mana, and a 3rd gives you access to 9. This ability to scale makes expensive colorless spells, such as Eldrazi, a real possibility. Glimmervoid doesn’t add extra mana based on how many Locuses you have in play, but it will make Cloudpost produce additional mana. With Vesuva to copy it, your mana will grow exponentially with every land drop.
This deck has a bunch of ways to cast an early Chalice of the Void on 1. Ancient Tomb and City of Traitors will do it on their own, and a Cloudpost into just about any other land (even those that come into play tapped) will make it happen turn 2. In an all-colorless deck with plenty of Eldrazi, Eye of Ugin and Eldrazi Temple add a ton of value.
Chalice isn’t your only early lock piece. Trinisphere closes the door on Legacy decks that rely on low land counts and cheap spells. A Delver deck, even with an answer in hand, may never cast another spell for the rest of the game. Storm simply can’t go off, but they also can’t cast cards like Lotus Petal to make it easier to deploy an answer like Abrupt Decay.
There’s also tons of artifact mana acceleration. This deck is looking to cast 10-drops, and even more expensive spells. At only 2 mana, Grim Monolith will add mana the turn it enters the battlefield, similar to Sol Ring. A turn-1 Cloudpost into turn-2 Cloudpost or Vesuva with Grim Monolith means you’re looking at 7 mana minimum on turn 3. Another Locus on turn 3 means you’re all the way home with 10 mana.
The other artifact acceleration spells are slower, but both Basalt Monolith and Thran Dynamo give you huge ramp numbers. Getting to double-digit mana isn’t usually easy, but this deck makes it look trivial.
With all of these artifacts that tap for 3 and don’t untap, Voltaic Key is a great option. It’s a ramp spell with either Monolith or a Dynamo in play, effectively tapping for 2 colorless. Using one of these artifacts will give you 3, the Key activation costs 1, and then you can tap for 3 more.
So you have lots of mana and ways to ramp, but you’re going to need to stay alive. You can get up to 7 mana on turn 3 without much of a sweat, and in a deck like Tron, this might mean a Karn, Liberated, but All is Dust is going to do more work in Legacy. All is Dust is also an Eldrazi spell, meaning that all of your lands ramp to it—both Eye of Ugin and Eldrazi Temple power it. In your all-colorless deck, this is a one-sided sweeper that also hits their planeswalkers.
Thought-Knot Seer has so many ways to come down on turn 2 it’s almost guaranteed. It doesn’t take too much interaction to disrupt many of the fragile decks in the format, and dealing with a 4/4 that early isn’t trivial anyway. Dodging Lightning Bolts and Abrupt Decays makes Thought-Knot a solid threat.
You also have all of the big Eldrazi. First off, there’s an entire playset of Ulamog, the Ceaseless Hunger. Ulamog comes down and exiles a pair of permanents, typically ending the game on the spot. With a number of ways to cast an Ulamog on turn 3, this is basically unstoppable, and the trigger doesn’t even care if the opponent has Force of Will. There’s also a Kozilek, Butcher of Truth and Kozilek, the Great Distortion to fill your hand and make sure the game is over the next turn.
If you love fast mana with the most powerful spells in the history of Magic, this is the deck for you.